My brother in law is thinking about them for rear surrounds (in the ceiling, regrettably) since there is no convenient place to mount them without "headbanging" (low ceiling) and the back wall is 35 feet away from the screen.

My gut feeling is that back wall would still be OK even at that distance but I have never seen a setup like that.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8