Hi Ddave,
I have done this very easily in CFS1 using EOD - I have no reason to believe that it will be problematic in CFS2 either, though I haven't tried it as yet. Use it to create your API files
You can find EOD at:
http://www.echos.ch/eod/It's as simple as checking a tickbox in the object options - I don't have the program in front of me, so can't be more specific. But it really is easy - if I can do it, eh?
For existing scenery objects that you wish to make crashable, I suggest creating invisible walls to position around them, etc. A little fiddly positioning them, but easy to do otherwise.
Hope this helps,
Pads
PS. You will experience occasional texture bleed through issues with complex scenery objects in CFS1 - there's not much you can do about it without getting very technical with the underlying scasm code that defines the APIs. Apparently you don't get the same problem in CFS2, though again,I haven't tried it yet.