This is a derivative of the paxtruder.
Main addition is the mount.

Keyword for the acrylic parts is no stress...
The base material;5mm cast acryl with a spacer plate of 1mm.
I used M4 nuts and bolts to reduce the stressing on the acrylic parts where the nuts are pressing it (larger contact area is better)
Also I redesigned the square cross connection a bit to get around the sharp angles, again to reduce stressing.
The cast acrylic parts are heated 1hr on 80 deg Celsius after cutting to reduce local internal stress.
The height is something to optimize, but since I'll have to laser cut the rest of the makerbot, I cannot test it properly yet..

I used nylon instead of the delrin piece, it does run quite smoothly..