[Cory]

I think your design depending on those tiny little L brackets to hold the frame together (In addition to the plate going across the rear) is going to prove to be too weak. That sheet on the bottom is not going to be very sturdy. At the very least I'd make those L brackets triangulated gussets. I'd recommend adding some real cross beams. Your frame is one place you don't want to have to ever worry about bending or breaking. If it weighs a little more, the peace of mind of knowing your base will be rock solid is well worth it, in my opinion.