The new EG4 BrightMounts have adjustable positions 25, 30 and 35o.
I originally planned to use 3x 4x6x12' and there was going to be a 3rd 4x6 under the back with the middle 4x6 centered. During my first build I realized it was plenty stable with two, with or without panels. So I decided not to add the 3rd which saved money on not needing more casters and 4x6's..
So I decided to leave them as a sort of outrigger to help prevent any possible back tipping. I have put cinder blocks combined with bricks under them and it really helps to lock them in place.
I stood on the middle 4x6 beam and jumped around some and it was plenty able to bear my almost 200lbs no problem. The weight is also spread across the beam and the panels weigh about 200lbs. I originally planned to add another caster in the middle for the added support but decided it wouldn't be needed. Again, saving on cost. I also figured if I ever noticed any sagging then I would go back and either add a middle caster or place a cinder block.