Anyone have a good idea where to find them?

I picked up the old Aerosoft DHC-2 Beaver this weekend and it sounds really great with OBIO's radial engine sounds.

The only thing I'm trying to find are some nice "thumps" for the main gear touchdown (something that sounds more "off-road" than the usual chirps).
I've even tried my sound files for some B-52s but they sound way too "heavy".