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.