May I recommend you check out the changes I made to the design on 22 Jan. They make mounting the bumper much easier!
Shoot. I already plasti-welded all of the parts together. I'll have to revisit after the next round of parts comes off of the printer and figure out the best way to cut things apart.
What is the next thing you are planning on revising? (I'll hold off on that one). I'm in the middle of printing the cyclotron now.
I did the same until I realised.... The problem is the holes for the bumper intersect the junction between the two synch gen parts, which means it's a bit difficult to drill.
Can be done though, I just drilled the bumper holes slightly below the junction. With care, you can drill al the way through and use some filler to tidy up on the inside to give support for nuts.
The outside doesn't really matter as the bumper covers it.
Next revision will be the cyclo mounts, this will not affect the cyclotron itself. I've replaced the four 'pipes' with two rectangles which faster to the cyclo from underneath.