[subtle71]

70short: Nice enclosure! If you have removed the gas tank, that is a nice solution. I am going to assume that pebbleboy is using a 12" sub that requires a lot of air space/large enclosure to perform. I originally did four 8" subs under my seat. They each required .33 cu. ft. for optimum performance. I had each pair sharing a .6 cu. ft. I have since changed to a pair of 10" subs that require .66 cu. ft each for optimum performance. If behind the seat is not an option for you, do your homework to make sure the subs work well in small enclosures. Also, either way, double check how deep the sub is physically.

Here's mine old set up.