I've been considering this for a while as a cheap solution to the "custom chassis" aspect of rock crawling or scale 4x4. I know it's a bit elementary, but there are a lot of possibilities for different lengths and adjustment, etc. Here's something I put together for a simple demonstration. Forgive me if this has been brought up already, I didn't find it anywhere else.
The whole idea behind this of course is to add axles which for some reason are hard to come by at an affordable price....SC4WD is manufacturing micro axles, LOSI has the micro crawler, and several others are probably available...but I can't really afford any of these...Any suggestions for cheap solid axles, even if they require lots of fabrication?