Tripod leg detent?

I'm beginning to design a portable darkroom that is basically a box on a set of tripod legs. I realized a little while ago that there was probably a standard detent angle that tripod manufacturers incorporate into their designs for the initial spread of the legs. I'm guessing that angle is about 15-20 degrees, but I don't have a tripod handy to measure.

Anyone have a tripod and protractor handy?

I measure 20 degrees on my Gitzo at the normal setting.

Thanks David.