Will a 12in JL W7 fit?
#5
#6
Might be able to fit a Sundown sd2 12. Most other 12s are going to be too deep. Shallow subs suck, with a few very expensive exceptions. One combo that seems to work well is the fox acoustics single 10 box and alpine type R
#7
wouldn't be enough airspace for a JL 12w7 under the single seat. Fox Acoustics makes a box for 2 10's and if the mounting depth is correct, you could fit 2 sundown SA10's. which would be pretty loud depending on the power you're sending to them.