Ah, well, its not though. The front skid on the Maxx is angled upwards, and the bulks mount onto it which tilts them back, giving them the kickup angle. Where the upper-plate of the Gmaxx chassis (or chassis plate of a stock chassis) attaches to the bulks there is an angle to the bulks so that everything lines up like a jig-saw puzzle. Side by side though, there is no difference in shape really between the front and rear bulks- but they obviously arent interchangeable. I think these pics show what I mean best:
Front- imagine it is tilted backwards a few degrees.
Rear.
With the Xtreme chassis the skids are built into the chassis, and there is no kick-up to the front skid- I guess when you tighten the bulk into posistion though the skid will flex upwards to the correct angle?...