Did you think that the newer seat wouldn't fit in the back, or did you try? I'm just curious if you tried it both way and decided it would be a better overall deal if you used the older frame with just the new seat cover on it. Thanks!
Are you asking about the rear seat bottom, or the backs? I've seen a few pictures of the seat bottoms where people have used the newer seat fabric and installed it on the Fox seat frame. It is not a perfect fit, but it can be done, and IMO would need to be professionally restructured to look 100%. To save money I just used the whole 2002 seat bottom. That way I retained the SN95 "bucket seat" look instead of the totally flat look of the Fox rear seat. As I mentioned in the other thread I linked to above, the cushion needs to be altered on the bottom (foam cut away and metal frame bars cut down) to fit in the Fox space, and the car will need a 2x6 wall installed behind the doors across the car to mimic the SN95 cars if you go this route.
Another option a friend thought of is to use the Fox frame, but somehow cut out or form the bucket seat shape in the foam like the SN95, and then install the cover on the seat. That way you keep the bucket seat look and have it mount the same as in the Fox. Since I have not permanently attached the seat bottom, I might look into this option. But I know it would need an additional piece of seat material across the front edge to cover the foam properly and look stock.
As for the seatbacks, in a coupe you really need to use the complete SN95 seatback assembly and just screw it to the car with minor trimming of the metal seat frame. I have pics in the thread above of seats in a coupe also, at the bottom. The SN95 frame will not work in a hatch since you need a solid back to attach the frame to. That would require installing a solid bar across the car by the rear speakers to support the seat frame.
Really anything can be done, it just depends on how handy you are or if you want to spend a couple of hundred having someone custom fit the fabric to your Fox frame. I chose to go the cheaper, easy route. Mine took me probably about 3 hours total to install it, including installing & removing the seat bottom many times to figure out how much foam to cut off, and also figuring out how to make the Fox latch hardware work inside the SN95 fabric and foam. Certainly not a long project, but not a simple bolt on either. Also, I've seen a few pics where people have replaced the top fabric on the seatbacks with a new solid piece to eliminate the hole in the top. That gives them a good replica of the Fox seat backs, without the need to install the plastic trim or a headrest to "finish" the seats out.