I've seen a few guys running B16B pistons on B16A block.
But these tuners, won't let us know the whole exact pictures else you won't be doing the job at their place.
From what i gather but don't know how true is it, the pistons valve pockets are re-machine as safety margin if running high cams like jun 3 or toda c, and further works are also done on the head to clear the pistons.
With all these machining the compression does reduce a little but it is still way more than your b16a pistons.
My mechanic just assembled another B16a engine with B16B pistons for the coming MSS race, but he told this particular engine is tune for max compression and power and he himself doesn't know if it will last. hehe... He is doing some R&D work for track and not road use.
Last year, i did build a B18C engine with the B16B piston. Power was awesome!! But my old worn out Type R retainer broke and blew my engine.. hai.. no money built another monster engine now.