I put 6x9"s into my ra40 coupe but I guess its the same in any car, I just made a new parcel tray/shelf out of MDF as the original wasn't much good anyway. The MDF is think enough to raise the metal base of the speakers so that it fits nicley into the holes already there.
I completely agree with this...I also have an ra40 and ended up cutting the crap out of the metal...thinking back MDF would have been a better idea
Otherwise why not consider smaller speakers...or a set of good splits???