Hey Feasty,
Yea personally when I do a body for myself I would
- First align bodyshell to required position (using some cut down body posts) and mark body posts with a marker (no reaming at this point!)
- Mark wheels and ensure there in the correct position within wheel arch
- Now Liquid mask, cut mask, paint. leave to dry
- I then ream the body holes and trim to size, I then mount shell and check the previously marked centres are in the correct position and cut out the wheel arches to suit.
I like to fit my body so it fits a little more snuggly against the bumper without compromising the position of the wheels within the arch. (I find it stops the top of the arch cracking quite so much when you crash LOL)
Hope that all makes sense
Have cut out before tho and its not much of a problem, just dont like the flapping lol