That is a cool idea, I haven’t tried it. One thing I know others have done, is they used bass shakers, if you just want the tactile feel. But if you want the bass frequencies, those wouldn’t be any help at all.
What about a small box under the driver’s seat using <b itemprop=”name” style=”font-family: inherit; font-size: inherit;”>Dayton Audio DCS205-4 8″Dayton Audio DCS205-4 8″…Just<b itemprop=”name” style=”font-family: inherit; font-size: inherit;”> looking to add some lower frequencies, nothing that crazy.
Your 8″ is deeper (4.23″) but has more power handling, digs deeper and has more xmax. Grabbing an optimum box size, that’d be 0.82 CuFt, but a 3″ port would need to be almost 19″ long. Now, since this is under seat, you could run the port outside the box around the perimeter. No one would see it, especially if you paint it black. Fb and F3 = 33 and SPL is already up at 88.6 DB (2.5 more than the Dayton above) so you’ll get more out of it.
I have not put any of these into WinISD yet to check for actual Xmax, port velocities, or anything else, so feel free to check my info. I actually encourage it.