F-type convertible subwoofer ideas?

Like many posts I’ve read, I thought my F-Type’s pricey Meridian Surround system was broken (amp or speakers or both) when I purchase my 2016 with 15K miles. It was hard to believe such an expensive option would break in two years, but even harder to believe the poor sound was normal. After more time to adjust, settings made a minor difference and the revelation that much of the output is triggered by roof-down sensor makes it acceptable, but not great. I find missing bass power under all conditions, but especially roof-up.

I find powerful bass a necessity, not for playing music loudly, but for playing it softly. Adding a better positioned, more powerful sub seems like an obvious option.

The F-type convertible’s small size is a challenge to add bass in a way that can be heard. The rear speaker enclosures are a candidate for more bass by migrating them from a surround function to a more primary role, via wiring or new speaker hardware or both. But my seat-backs are generally almost touching the upper carpet behind them, nearly blocking and acoustically sealing the rear grilles most, if not all of the time. Not optimum IMO.

My thought is to add an 8" powered sub under the passenger seat and run a left & right feed from the lower door speakers with min or no crossover filter, as these feeds would already be low pass filtered AFAICT. There are several high power, compact options that would fit. I’ve installed similar subs in larger cars with easy, fully transformative results.

Question: Has anyone tried this approach, or similar, in their F-Type?

Hi Sandy
I know that this threat is from 2018 , but maybe you are still interested in my answer.
After changing all speakers in my F-Type, even those in the rear , I was still missing that little punch ,especially at low volume.
So I had the same idea as you.
And I found a very compact sub with 8’ or 10 ’ with only 5.5cm high ( Ampire 10SL or 8SL)
You may install it under the seat, but you have to take care to never lower the seat too much, as this will distroy the sub.
So I decided to buy the 10’ Version an to install it behind the passengerseat. Huge difference !!