I think that the reason for the coplanar requirements is that the tiles lap each other in the up-down slope direction, but only abut one another in the perpendi

I think that the reason for the coplanar requirements is that the tiles lap each other in the up-down slope direction, but only abut one another in the perpendicular. There's no interleaving or joining or flashing in that direction. Two abutting panels land into the same clip. Around penetrations and edges there are non-pv fractional tiles, and all of the ends edges and ridges etc are done with sheet metal. Leaving too much gap will get stuff underneath the tiles and also make them more susceptible to being removed by wind or exposure of the membrane to UV and other things it's not tolerant of. The real waterproofing layer is the membrane that's put down first. There are higher numbers of clips on the panels/tiles for high wind areas. If I was baller enough to afford this I would definitely invest in a continuous insulation roofing system to go on first.