At least with the 2DR you have to take the rear seat out. The front seats could stay in, in theory. It would be very hard to tuck the carpet under the center console, and just to lay down right. I suppose if there is a will there is a way, and people have done it before. Taking the front seats out, especially the first time with the super tight factory bolts isn't a walk in the park either.
SMALL NOISE FROM BACK
I just thought of something. I did notice when I first put the hard-top back on a low whine when above 35 mph from the rear. I think it is from the gears in the rear diff. It sounds about like a slightly squeaky computer fan. At first I thought I had the radio on super low. With the radio on you would never notice it. I have a strong hunch that if I had left the sound/heat deadening goop in the back it would cover that sound up. If you want to see what the sound is like I recommend taking out the 3 rear carpet panels (both sides and under where the rear seat goes). Those panels would be very easy to put back in.