I wouldn't worry too much about trees. If you're doing a Vietnam setting a pranged
UH-1 in a rice paddy would be an excellent subject. There are photos in the Squadron
Signal UH-1 in action. If the pilot was proficient and a little lucky, he could get a busted Huey down without doing too much added damage. In addition to the obvious battle damage (if he got shot down, some of this would need to be in the vulnerable engine area). Sometimes the rotor blades would flex and take a chunk (or totally sever) the
tail boom. Simulating damage to the aluminum skinned honey-comb blades would be tough.
If the bird hit a dike the results were often catastrophic. To simulate this I would build the model and then drop it on the kitchen floor and jump up and down on it a few times.
Pour the results into the rice paddy.
If fire followed the crash just build a portion of the vertical fin and tail rotor and plop that down at the end of a pile of ashes spread out in the profile of a Huey. If you want to be
really accurate put a scorched replica of the transmission somewhere in the middle of the ash pile.
Aside from the wise___ remarks, downed Hueys often had some of the plexiglass busted out or the skids spread from a hard "landing". A rice paddy setting will give you the opportunity to pose some grunts on the dikes and crew members or rescuers in the water.
If you go to the VHPA website and click on some of the unit links there are tons of
period photos which could help.
Just talking about this has me thinking...