Calibrating a 45mxt, regardless of the lens you're using, should not be too difficult even for those who are technically challenged. I'd try calling the technical assistance at Beseler - they can lead you through it over the phone.
The weight of the head on this enlarger is borne by the chassis, which is extremely rigid, not the lens stage as you have surmised. Think of the 810 conversion for your enlarger which weighs significantly more than your color head. Plenty of photographers who shoot 8x10 and don't have room for a floor-stander resort to this solution, without experiencing alignment issues.
Are you sure you have the adjustable struts at the right height? 3/4 of a turn out of wack can result in an mxt that's out. This detail is often overlooked by mxt users and it's essential for proper alignment when using this enlarger.
That said, the LPL is on it's way and will replace the 45MX as my main machine by the end of next week. In regards to ease of use when doing things like multiple grades on a single sheet, the VCCE head will be a nice step up from the 45S head in terms of ease of selecting filtration on more complex prints. Not to mention I can use my 150 Apo instead of my regular 135 Rodagon when doing 20x24's from 4x5 negs.
I still think a well tuned and setup 45M series is a great value enlarger and I will not only keep mine but likely get a second one to pair up for workshop participants. But for my needs and considering what I have invested in everything else in my workflow, it makes a lot of sense to upgrade my primary enlarger for the long run....
I believe the spec on the strut set-up calls for an inside angle of 85.5 degrees or 86 degrees, can't recall which one. Beseler tech can provide you with the factory spec should you desire to confirm this.
Regarding flexing stage.... the mxt is unusual in that bottom half of the negative stage has a spring-loaded opening to accept the carrier. Notice how when you open and close the negative stage you are not lifting the weight of the head at all. You don't have to be a mechanical engineer to plainly see that the weight of the head has zero effect on either the lens or the negative stage in this design. It's clear as day man! However, if you try to calibrate the negative stage without a carrier in the closed position you will experience alignment issues.
The saunders is a pretty slick enlarger. I've used them in rentals before - nice negative carrier. But unlike the Beseler, they cannot be aligned without major cludging - think machine shop retrofits (and you think you were having problems with the mxt!). They are permanently "factory aligned" which is why I don't care for them.
I agree a 45VXL would be a nice step up, and better than the 45MXT or any Saunders. I've used all of these, and have a 45VXL at home. It has numerous alignment points, and can be exactly aligned (using a parallel) even with heavy color heads. I don't know the height offhand but can measure if need be.
good luck, keep us posted
Strange problem you're having with the Beseler. Too bad. I guess you've already got the Saunders. Beautiful machines, except for the fact that you can't align them; that alwasy did my head in. The two that I've used were out of alignment, and the only option was to use shims. I use the versa lab tool as well. Love it.
The later Beselers, after the original 45M, can align the negative stage to the base easily with the supplied hardware, which allows back and forth and side to side motion of the whole focusing rail. You need an adjustable lens stage to finish the job. Zone VI and Delta both make (made) one in Leica thread size. However, making your own for any size does not take machine shop expertise. (Briefly) Take two Beseler lensboards that hold your lens and clamp together. Drill three holes 120 degrees apart of tapping diameter for three machine screws or allen screws around the hole. Tap three holes on one board and re-drill screw clearance holes on the second board and assemble a sandwich with the board with clearance holes board holding the enlarger lens and the filling of the sandwich a piece of dense foam with an appropriate circular cutout, and screw the two together. When mounted on the 45 you can now easily align the lens stage to negative stage and base of the enlarger with a screwdriver. If you are using a glass negative holder you can align in seconds for any print with the Versalab laser thingy. Unfortunately, for the Beseler 45, you will find that you have to do this almost every time you change the negative height! (i.e., you can nitpick if you want to - for 4x5 this probably will not improve quality as much as you hope. Alternatively, by obsessively aligning you can shift blame of any technical shortcomings of your prints to some other cause.) If you are using Cold light or a color head and you are somewhat handy, you can remove the upper bellows and use 1/4 inch plywood to make a box to hold the head, which screwed upon the upper negative stage will make the upper assembly more rigid.
As regards the Saunders, you can shim the column to square it to the baseboard as measured with Versalab bouncing off a glass negative holder. Unlike the Beseler, this fix will probably work well for a range of heights, but make sure your baseboard is as level as you can get it before playing this game. The lens stage is "factory aligned", which means that, by the time you can get one you can afford, it is not likely to be very well aligned. Nonetheless, on the later models, the fixture that holds the lensboard can be removed and shimmed and quite likely an adjustable lensboard holder could be fabricated, although I have not tried this. The various rollers that hold the head in place on the column have to be clean and in good adjustment (they are adjustable) for this to work at all.
Summary: Beseler easy to adjust but seems to need it constantly; Saunders maintains reasonably constant alignment after some fairly tricky and time consuming fiddling. This is my experience based on owning one of each.
As far as the issues people have with the Saunders, it's the way it goes, some are perfect, some are not, what else is new? The thing with the 4550XLG is that aside from a L1200 with a proper VC head, it's one of the best out there, so trying to pin down a VC head because it often has one as mine will. I have been talking with John Sexton on and off for a couple months about these enlargers. It's not going to be that hard to align it, I have all the tooling, use aluminum tape for shimming for other things. The goal is to get it aligned and get to work, not keep futzing with it like the Beseler.
I need as much consistency as I can get and since putting the color head on the 45MX, I am not getting it. I'll get it figured out and it will be great for students...
Once they are aligned, they stay aligned. Welcome to easy street.