The tubes are really only for the azimuth and elevation of the system. So to change the tubes to a different size you should only need to change the ball bearings the tube uses, possibly the 3D model for the ball bearing to be held in (C1010-3 and C1011-3), the hole in the metal that the tube comes out of, shield that goes over the tube to cover the hole in the metal and at the ball bearing (C1083-1 and C1022-3), and the two gear setups (the one for the worm gear, C1020-1 and C1021-1, and the rotor encoder/endstop, C1040-1 and the insert for it C1041-1). Basically all of the items listed on this image File:A1030.png - SatNOGS Wiki. As long as you aren’t going bigger (which might cause an issue with the grub screws), then you should be alright. I also saw someone looking into using extruded aluminum (not sure if it was 2020 or something else). If that it was just a matter of making adapters or new 3D Parts.
I was thinking about setting up a kit as well. I have a couple other Amateur Radio operators around here who are interested in doing satellite communications. Since AMSAT doesn’t sell the WRAPS by Mark Spencer, WA8SME, there aren’t much options aside from rigging something together or spending a lot of money for one. So I am experimenting with this to see if it will work out. I don’t think any of them have a 3D Printer so I will most likely be making those parts.
Anyways, that is what I believe would need to be changed. I won’t say that is 100% what needs to be done, but it is a good start.
Edit:
Just to throw out there as well, ka4jwb modified the parts to use USA PVC Pipe instead of the aluminium tube.