[Rick TYler]

That's going to be a seriously strong chassis. Once you get all your components mounted, get yourself a 2" spade bit and whack some speed holes down the center line of those 2x6s. Remember, the stiffness of a beam goes up as the fourth power of its cross-section. 2x6 studs are really, really stiff on edge -- and the breaking point is also very high. You can easily remove material without compromising strength below a danger point. That 3/4 ply is heavy, too. Do you have a piece of 1/2" you can use? You really don't need that 3/4.

On the other hand, a cheap, strong chassis. Have fun!