Convertible Speaker locations

I had an idea for how to get some sound in the back seat area. The front is easily solved with some custom kick panels. But the back is the problem.

It occurred to me that I could make some custom speaker boxes that fit the area at the bottom, behind the convertible side panels with the speakers aimed straight up. I'm thinking the sound would come up and out of the area around the convertible top linkage. I think it would sound OK as long as the convertible top boot cover is not snapped on. Since the high frequencies are more directional I was contremplating some tweeters mounted in the recessed area just above the armrest. That means cutting a very small hole in the convertble side panel, which makes me cringe, but at least it's not a very noticeable location.

I measured the area and it's tight on width. I'm thinking a 5-1/4 might fit. That or a 4x10. The 5-1/4 might be enough since I'm planning one or two powered sub woofers under the seats for the bass. I just picked up 2 Sound Ordnance B-8PT powered subwoofers on Craigslist. They're shallow enough to fit under the front or the back seats.

Does anyone have an opinion on speakers down under the convertible top linkage? Will they sound OK? Should I be worried about dust and dirt collecting on speakers that fire straight up?