alpine type r 8’s box volume

whats up, i just bought myself a 2011 nissan frontier 4 door crew cab and now im in a bit of a situation. im trying to plan a system and in looking at sticking 4 type r 8's under the back seat in a custom wood/fiberglass composite box. the reason for the type r's is that i know they can get loud but i also know they prefer ported boxes. i figure i have at best 1.2 cubic feet under the seat without having the box stick out from under the seat too much. alpine recommends .3ft^3 per sub sealed which should work out nicely but they also spec that box as having a f3 of 53hz, so if what i am thinking is correct, that box basically peaks around 53hz, is this correct or am i way off base? next, this will be for the most part a sound quality system so im really just looking for a nice smooth bass that has good response below 45Hz and im worried that these box recommendations just wont come close to what i need. maybe my expectations are too high being that im switching from a single ported 18 to a few 8's sealed but i really think that i can be satisfied so long as i can get the box right. i would be willing to drop a sub or two to get enough airspace for the rest of them to properly put out. ive never been a fan of sealed boxes, over the last 6 years that ive been installing ive build many many nice sounding ported boxes but i have next to no experience building sealed systems, which seems completely backwards but its true and im kinda scared that i wont like it. oh, and these will be coupled with a diamond hex pro component set up front that will be bi-amplified off of an alpine pdx-f4. i dont have an amp picked for the subs yet mainly because i dont know for sure how many 8's im gonna be able to use. ill probably be taking the back speakers out all together and plug the holes. any thoughts or opinions on the matter will be greatly appreciated

Why dont you go with two 8's in a ported box? Alpine says anywhere from .15 to .5 cu. ft. for sealed and anywhere from .25 to .60 cu. ft. for ported There is a ported box listed in the owners manual that is listed at .70 cuft. I am sure you could scale it down just a bit to meet under seat space reqs. f3 of 31hz sounds like it is in your ballpark.

i dont know, the problem i have with making a ported box under my seat is not that i dont have the airspace to put two 8s ported, its more about how i dont have the physical dimensions under my seat for a proper port tuned low. it is possible but im trying to keep it simple. you cant just scale down a ported box, small changes can have big effects. less airspace means i need a longer port to keep a low tuning frequency. a longer port means it takes up even more volume inside my already small box. that .7ft^3 is for one sub ported, two subs would be 1.4ft^3 and i just dont have that kind of space. if i build this box for 2 subs then my port would pretty much end up on the opposite side of the truck and alignment is everything with ported boxes. not saying that it couldn't sound good but ill think about it.   i hate trial and error

eh, ill try two 8's ported and see where that gets me.