I must admit making a new slot and the slider were the hardest parts especially as the slider with the lens cant be used. I had a 2 inch square of alluminium about 2mm thick that I knew to be dead square all round, and I cut 2 triangular pieces off 2 of the square corners. I forget the size, but they are about 3/4 inch high, 1/2 inch at the base, and the point at the top flattened off. These triangles happily sit on a machined ledge within the bore, and if memory serves me well, I put them in place inside, opposite where the lens slider is. What I suggest is you do a lot of staring at the components! (I did loads) because I found I had to completely ditch any metal on the moving helical that wasnt going to be used, because I reversed it, to give a square 'platform' to mount a lens panel onto. Also having 4 or 5 (cant remember) starts on the thread wont help either.
As for securing these triangles in the bore I used good old epoxy, and because I was essentially fastening something flat to a round, it meant epoxy could go round the back, and both triangles could be well and trully stuck in place. As a guide to the distance apart these triangles are, I decided to copy the olympus gap. If they are square and placed well they should end up giving a very decent slot for a slider, and for the slider I cut up some brass (off a picture frame plate) that was about 1.5mm thick, bent it to 90 degrees and filed away till the long part had a 'neck' with a wider bottom - very much like the one from the oly lens. The hardest part was to get it to 'slot width' at the bottom, without it having any play. This little slider was screwed into the holes left by the oly slider.
I have to say working it all out nearly drove me mad, but so far both focusing mounts are behaving well, and I have real faith in epoxy, as I cant see how any screws etc could have been used. Also near the end of all this I found there is a seperate threaded part to the lens (under the rubber ring) that made getting infinity dead easy.
I think whatever lens you use you are in for some fun!