I've always wondered the point in such setups (as opposed to mounting them on a systems type board).
For me a fingerboard is just that, a method for isolating the fingers (as best as you can). A campus board is a completely different beast (again, IMO) where I'm aiming for explosive power, lock off and contact strength. Is there a benefit in combining the two?
If I was to build a setup as you describe, I'd have a decent angle so that the inevitable hip dab (or tw*t in my case) doesn't occur.