From the looks of it, looks like the batt compartment is smaller than the slash 4x4. I know by looking at the 7 cell hump pack in there, that most of my lipos will not fit...
Also no room to "cut out" the back of the chassis like the 2x4.
Sorry to keep you hanging, 1Slash hit me up for the dimensions last night. Here's the scoop on the Stampede 4X4's batt tray dimensions:
L: 142 mm
W: 48.5 mm
H: 23 or 25 mm depending on the position of the stock included hold down. Each side of the strap is labeled so you can see which orientation gives you 23 and 25mm. --Pete