Both front and rear port placement options are fine. The thing that's important on the towers is the vertical position. Do not move the vertical position of either the port or the woofer because that would change where standing wave nodes line up. The positions chosen minimize response abberations from internal standing waves.The port is fairly large and so velocity is rather low. But I'd still suggest six inches of unobstructed area surrounding the port. That said, I've got mine shoved clear back against the wall, with exactly two inches between the rear baffle and the wall. It sounds just fine like that.