Lol ^^.
Thankyou guys, my brain is buzzing with ideas right now- kinda makes the truck look more 1/5 scale with the larger/ wider body in a way, which is kinda what Im after in terms of appearance. With my hoofing great big tyres, the truck is very wide, and quite long anyway, so a larger body 'fits' the look better, if you get my drift.
Interesting thought I had though, thinking back to my TXT-1 days:
http://www.robotwars.00server.com/specs.html (TXT-1 dimensions)

Gmaxx dimensions.
I think I figured out why my truck looks so wide compared to its length- the TXT-1 was bloody huge, 2 inches longer in fact. I think I need to extend my chassis somehow to get the proportions better, and still use the corr type shell at the same time...
Winter project me thinks