1974 MGB, fitting a sub?

[jordan.guess 1]

Okay so ive been doing loads of research on parts-express and so forth on finding a sub for a 1974 MGB. I really only want something super small and getting something for better sound quality than just two 6.5's in the doors. Behind the seats is a bit of space but want to keep mostly the stock look. However, there is a compartment where a second battery used to sit that is no longer there and I think I could find a small box in there. I measured the dimensions and can get about .15-.18 cuft gross airspace without making anything look out of the ordinary. I havent found much for the 8 inch woofers or subs that will suffice in that airspace, however there are various ones in the 6.5 woofer range that may work but I was hoping i could get some advice on here for direction. Also I would need a small cheap amp to match with whatever sub I can get in there as well, so information on that would be handy. Another thing I meant to mention is that this is a convertable with a soft top, so im sure that may effect the SQ as well. Your help is much appreciated! thanks!

[Impious 1,476]

By the time you account for the enclosure material and driver displacement (assuming you will have the driver in the enclosure & not inverted) I don't see that airspace feasibly working. Honestly in a convertible I don't see a single 6.5" "subwoofer" having enough displacement to make the endeavor worthwhile. Even a single 8" driver is going to be a questionable improvement.

IMO you need to find more space somewhere, maybe find somewhere you can run a larger diameter driver (i.e. a 12") infinite baffle so you don't have to worry about enclosure airspace, just enough room to fit the driver itself and a baffle?