I spend a lot of time at many different ranges, and while the OP's backstop is small, for someone who is very careful, and is doing something limited like sighting in a rifle a couple of times a year, it would be okay.
I'm going to be building three different backstops on my property this year. The main one is going to be a 50yd range behind my barn. The plan is to stack 2x2x8' concrete blocks five high (considering six), and six wide across the back. Then I'll add more blocks on each side of the backstop to create side berms, again five (maybe six) high, but only three deep. This will give me a U-shape backstop that is 48' wide, with 24' long side berms, and then I'll backfill with dirt in front of the blocks. The area behind, and on both sides, of this is heavily treed, with no houses within at least a quarter of a mile (only one or two, with the rest being more like half a mile).
The second backstop will be my 200yd range. It is essentially a 30ft wide cut through the trees, and I'm going to build a wall with railroad ties, and telephone poles that's probably 8x8', then backfill in front with dirt. The area behind that is extremely heavily treed, and there's virtually no way I'm missing an 8x8' backstop doing the kind of shooting I do.
The third backstop is going to be a 25yd range that I only use as a backstop for accuracy (off a bench/Ransom rest) and chronograph testing. I plan to make it similar to the 200yd backstop, but it's going to be set up so that I can shoot to it from one of my barn doors. I'm going to put it in a different direction than the 50yd range, because I want to have the best sunlight possible when doing accuracy test...which means I need two different directions for different times of day. Again, I'm not going to miss an 8x8' backstop doing bench accuracy, or chronograph work, so I'm not worried about the height, and it will have heavy trees behind it.
So, one range for "dynamic" shooting (I'm a USPSA shooter for folks who are familiar), and two backstops for static, deliberate shooting.