You can install a Robbins zipperless top on a Miata with a Boss Frogg Double-Hoop roll bar
I installed the roll bar with a friend, then had a professional installer do the top. I had called around to find out if the zipperless top would work with the roll bars, and could not get a definitive answer, so thought I would post here for posterity.
The window rests on part of the bar when the top is down, but that can be padded with pipe insulation. Works like a charm and the top can be put up or down quickly and easily.