I dont know what you mean by laying it flat on the ground, but i have it mounted horizontally in my trunk, right now it's not even screwed in, the thing is is that now BOTH amps are overheating, not just the sub amp, i know that mtx thunder 564 shouldnt get near as hot as it is, especially with the gains at less than half. Everything wired just fine...rly pissin me off. Ohh and the grounds are like 2 inches apart, that isnt the problem is it?