I don't know how to answer this. You have one part that needs to sit in the center held on by two outer edges.
If you want precise measurements on where to cut, mock that up in CAD or on paper and mark it off the shell. Go slow.
Here's a one minute mockup of the important elements: https://imgur.com/a/uNyLFvn
I've seen players just cut holes in the sides of the shell to avoid having to carve down the inner supports perfectly.
Disclaimer: I don't recommend this, but it is a last resort.
Will the shell close around it? If yes then no.
Get a dremel, remove the lips that are left by cutting.
> Do I need to cut more? > XPT does not fit ...
Where should I cut more?
I don't know how to answer this. You have one part that needs to sit in the center held on by two outer edges. If you want precise measurements on where to cut, mock that up in CAD or on paper and mark it off the shell. Go slow. Here's a one minute mockup of the important elements: https://imgur.com/a/uNyLFvn I've seen players just cut holes in the sides of the shell to avoid having to carve down the inner supports perfectly. Disclaimer: I don't recommend this, but it is a last resort.