Solution for underseat sound system?

So I've been thinking a lot about adding 2 more 10" to my system but I want them to go under the back seat. I currently have 2 shallow mount 10"s and a box behind the seats of my crew cab. don't get me wrong, they sound great as they are both 600RMS subs, but I want to "beat the block up" as the rappers say. My buddies full size kicker 10"s at 300RMS each hit harder than my shallow Digital Designs 10"s at 600RMS each.

Here my predicament:
1. Zero space because of the foam under the seats. I've seen on YouTube and on some websites that you can cut the foam out pretty easily. They also make custom boxes to put in place of the foam but the ones I've seen are roughly $500 just for the box.

2. If you do cut the foam out, you can only fit shallow mount subs with a mounting depth of about 4.25" and that will mount flush to the bottom of your seats.

Solution?

I noticed there are metal bars/brackets for where the seats meet the cab and mount. Now, tell me if this makes sense:

If I get either some spacers or washers of some kind and raise the entire back seats up 1-2 inches, my mounting depth should increase because of more space, correct? Sounds pretty simple in my head, might make the back window a little smaller but I don't think it would hurt anything considering I have a back up camera or its usually rolled down anyways. Might have to get longer bolts for the seats, but I think that would be minor.

I want to put full size 10"s under the seats, and the smallest mounting depth I can find it 5.25-5.75" and I'm ok with that.

So in theory, my idea should work. Unless raising the seat height is much harder than I'm anticipating..... Does any one have any advice, pointers or information to tell me I'm an idiot and that my idea won't work?

 

I'm putting a pair of 10" shallow subs behind the back seat. Did a easy mod so I can fold the setback down to access the area. Not a lot of room but should be able to get two .70 CF enclosed boxes back there. Will post Pics when boxes are done and installed.

 

I would love to be able to just fold seat back down to access area behind seat. Not sure what the heck Toyota was thinking with not putting a latch on it.

 

Easy mod for that if its a double cab.

https://www.tundras.com/threads/rear-seat-fold-down-mod.8153/