Those are tough birds.......I'm assuming that it went down at a low level?
I would study as many real crash pics as possible.......it's better if you are working from a real situation.
I would thin the plastic on the body where it would bend and crunch and try to get as many 'sharp' bends and twists as possible, then cut the interior parts to fit or bend with it.
At a low level impact there really would not be that much damage and you could also rough up the dirt or building materials to help hide some of the helo damage.
The thing that makes or breaks a 'downed' helo dio is the blade damage.....its hard to get 'modern' blades to look just right.
Oh yeah....don't forget.....loose or seperated panels always looks very cool too!
Good luck!
Straighten up and fly right.....