Its more the big plumes of smoke that they generate after they have been destroyed that causes FPS drop. A few vehicles scattered about is not something that would be an obvious target. Well thats my thinking anyway.

Name the planesets and the location you want to use (southern / eastern England) and I'll whip you up a map.

Edit: I see you spelled it out already :)

Thanks Bliss, thats very much appreciated, we will give you a credit on the server and a link to your server as well.