I grew up in a confined neighborhood. One of the guys living behind us shot a recurve and seemed to solve this problem. He built a small tool shed type building on 4" x 4" posts elevated off the ground about 10", probably to keep mice and snow out. Overall, I would guess (only a guess) it's dimensions were 24" deep by 50" wide by about 70" high. Inside were placed three large straw bales. He used T11, shingled the roof and painted it the same color of his house to blend in with the neighborhood. To add to the effectiveness, it was placed parallel to the open length of the adjoining backyards since they were seldom occupied unless grass was being cut. The split doors had additional plywood facing on the inside, swung out and were propped open to make an even bigger "gull wing type" backstop. Imagine it cost a bit, but I recall he used it many years with no problems. Wish I had a photo of it, but he moved several years ago and evidently took it with him.