There are several styles in use. I prefer those that have a wider part in front and a narrower part in back, with a large radius curve at the inside corner of the transition between the two. I think that it is easier for a short man to shoot from a stool that has been adjusted up than for a tall man to shoot with a stool that is to low to sit on comfortably. The benches that I a most familiar with are 34" tall. I would go no shorter. The back portion of the bench, what I refer to as the tail, should be about 16" wide, so that shooters' elbows do not hang off the far side. Much wider than that is just wasted material. There is less noise if rifles' muzzles extend in front of benches tops, so it is a good idea to have the front part of the bench no longer than about 24" (parallel to the rifle). I like the front of the bench to be a couple of feet wider than the tail, evenly distributed on either side. More does not hurt. Much less tends to crowd your equipment if you are feeding a rifle with the loading port on the same side that you are. The length of the tail can be as much as you want. Probably a foot and a half would be a good minimum for the length of the straight sides. the large radius that I spoke of can be 11-12" and consist of a quarter circle. If you add it all up, you get a minimum of 40" across the front and 4 1/2' long. I would make sure to space them as wide as your setup allows. What ever you decide on on paper, build a mockup out of scraps and have several people of different sizes try it out, shooting. To do this properly, you will need an adjustable stool. You can build benches that are smaller than what I have suggested, but why would you want to? The other detail that I would stress it that the benches need to be totally wiggle free. If you need any help with that, let me know. The other thing that I will mention is that it seems to me that a lot of benches have been built with less than ideal top shapes because their builders did not know how to easily form what seemed to them to be complicated shapes. I can help you with that, and show you how to easily construct forms for the most elaborate shape with relative ease, and economy. Going on three decades ago, we built a set of 42 of the most difficult to build benches that I know of. They are the same design that is at Visalia (that has 28). They are still there, and they don't wiggle at all.