Attaching sub to back wall of the cab?

I just bought a Kicker Hideaway this morning and it arrived this afternoon (gotta love Amazon Prime). I have one in my CC and it is plenty good enough for my needs but this one won't fit under the driver's seat like it does in the CC. Is there a way to attach it to the back wall of the cab on an RCSB or should I be looking for another way to mount it? I like the storage bin behind the seats and I'd prefer to keep it in there for tools & such.

I have another question also....I have a Kenwood head unit in my CC but I'm keeping the factory 5.0 in this one. My Kenwood had a sub-out but I'm assuming the 5.0 does not (6 speaker setup). The Hideaway has connections for both left & right, + & -, do I need to splice it in to both the left and right rear speakers or will one side be sufficient? I'm sure its obvious that I know very little about car audio, I have new Infinity speakers coming on Wednesday and would like to get it all installed after work that day if I can.

That's odd that it won't fit, I'm sure there are quite a few people with regular cabs that installed it under the seat??? Hopefully one of them can lend a hand with some install info.

I may be able to get it under there if I loosen the seat bolts, I'll try that if a better option isn't available.

I plan to do the same shortly. My plan is to mount it to a piece of MDF and secure that to the back wall of the tuck. Yes you will need to tap the left and right speakers.