The GP6 has a different slide profile and the holster may not work well with the newer GP guns.
I have a DAA Racemaster, I got an insert for the X-calibur and with a little sanding it works great with my X-trim. They are expensive though, for a more affordable kydex holster you could wait, Blade-Tech is supposed to be making them soon OR message member Canuck223 - I believe he is making and/or importing holsters for the GP series.