I have one in my Tundra. I think the mounting depth was about 4 5/8" or therabouts. I tried the Rockfords but went to the JL Audio's which I think sound a bit better. I guess you could use a spacer but keep in mind that it still has to keep the enclosure sealed and might get rather close to the bottom side of the seat when down. I think you need that small air cushion between the sub and seat. Also, if it's too deep in the enclosure you lose that space which might impact the performance of the subs themselves. They need a certain amount of enclosure space. I really like the JL's. They have plenty of "thump" for my tastes. Hope this helps...
