Since purchasing my son an E-Maxx a couple years ago, we have converted it into a sort of a Summit/Maxx hyrid by adding spools to both differentials, a wide ratio 2-speed kit and a set of Trenchers. However, the shorter wheelbase has always been a hinderance crawling, and it just doesn't do as well as my Summit in that area. So, I decided to stretch the wheelbase 3 inches. I added all the length to the rear (so it is more weight biased to the front).
I basically just tacked on a 2nd chassis, extended the braces and added a 2nd skid plate underneath. Overall it turned out well, and the performance difference is night and day. It climbs very well, and is almost impossible to flip over when bashing around the yard. The proportions are a little out of whack, but oh well.