From advice given me it's easier to get hold of a late S2/968 complete hatch and swap over. That's what I did to my 944. Put a 968 turbo s spoiler on which is just slightly bigger then the bridge version. I had a look at removing the rubber spoiler but my screw fixings were rusted right in and the head just sheared off. I got a complete hatch off Ebay, it was quarter the price of a fibreglass kit. Took off the spoiler and cleaned. Took whole hatch to be sprayed to match body colour and the sprayer fitted the spoiler back on the hatch and sealed water tight. Collected and then just 4 screws to fit in and align. Thread with pics is here
http://forums.tipec.net/viewtopic.php?f=25&t=5097&start=0 And some more here
http://forums.tipec.net/viewtopic.php?f=25&t=34&start=390Maybe someone more technical then I can help more if you want to remove the existing rubber spoiler.
Good Luck, 944's look much better with a bridge.
Andy