To hold 10 pounds you don't need a 2x4 Chassis. It will add unnecessary weight to the thing an deplete your batteries faster when moving.
Alluminum will be ideal; but probably too expensive. Simple 1/2"x 2'' or 3/4"x2" boards will probably work fine for the frame at a fraction of the weight and cost. You can just reinforce the corner joints with triangular pieces of plywood.
The dimensions are not for the weight itself, it's more for what I'm trying to put on there. So you're suggesting aluminum, won't that be bad incase of a grounded wire or something static??