It ain't me, but my lil subwoofer sits under my seat and....well...it rattles the licence plate - welll something that rattles :wink: and makes those cool (to me anyway,) buzzing and vibrating "noises" when the seat is closed. My pillions have said that they actually feel it up thru their rump..and in some ways, I do too. I do not, however like the way it takes up space under there, but I can still fit an 18 pack of brewskis, and, sans the beer, I can fit my xxl full face helmet and big leather jacket with space left over - no prob!
I know that this isn't the answer to your question but...just thought I'd toss in a "knowledge point."
I think the person who you are looking for is an Italian dude that has done his chariot up nice!
Ciao,
Pete