I started by dry fitting all the parts. The fit of all the ABS-on-ABS joints is a bit rough due to the surface finish but are not too snug. I may sand the nose cone shoulder to make it smoother. The motor retainer required some Dremeling to allow a C6 to fit well. I also had to grind the inside of the motor mount near the motor block.
I was worried about the thick motor mount but, barring cutting the entire middle section out, I can't see that I could save that much weight. I drilled one big hole in the middle and discovered what I should have realized - that the structure is basically hollow. So, it is now attached with 5-minute epoxy.
My next worry is how the ABS will handle ejection gasses. I could ask on TRF but decided to put a cardboard buffer in the lower body. The ID is almost 29mm so I cut a short piece from a thin wall tube, sectioned it, and slipped it in.
BUT, what is really scaring me is the prospects of painting this thing. Even if the smooth body sections were sanded smooth, much of the painting is on ribbed sections. These will be hard to mask.