Once upon a time I had a PDF on small arms range development from the USAF. I used it when we refurbished our range. The google machine may find it floating around somewhere. It did have extensive information on overhead baffles as discussed earlier here.

I did run across a single point range some time ago which was genius. The fellow had constructed a backstop slightly wider than his target frame / holder. Extending from this flat backstop he built two walls extending in a sharp "V" for 6'. At its mouth it couldn't have been 6' wide at the most. Taking into account that it was at least 2' wide at the target due to the flat backstop. This one was made of rough cut 2" lumber as outer walls holding fill dirt which was whatever the state road obtained when they pulled the ditches nearby. The insides of the backstops were then covered in old rubber conveyor belts from the coalmines, I assume they were to soak up rounds and save the lumber beneath them. I'm guessing it was less than a foot wide overall. It was the only time I'd seen a "V" shaped backstop and probably the best answer to a populated environment surrounding a fella who wanted a range in his yard.