Yes. My BEFCO BGS072 is adjustable. I would suggest you consider that in your design. Im not sure what my max is, but I would guess mine is down at least that much and does some serious cutting on my driveway. It is my favorite tractor implement. I have LONG gravel driveway.
Bearskinner used my build as his copy, his looks way better than mine.
The blades are 1/2 to 3/4 deeper than the side rails.
The blades are the same angle and about 30 degrees, it really doesn't matter much.
Use hardened steel , AR400 or better for the blades and they will outlast you!