Box>solid subtract > quad mesh question

Hello friends! Quick question: I've got an array of center boxes, and i'm trying to chamfer the ends of them all by solid subtracting other boxes that are rotated to give the angle. It works, but the subtraction triangulates a bunch of the faces that should be planar very finely. I'd like to have a model with only minimal (1x1) quad mesh faces to keep the file size down as i'll be rendering it.

Any tips on how to either alter the geometry to a quad mesh or do something different in the operation to get cleaner geometry?