Stx mounts don't work, or at least don't without a bit of work as the pins in the xtr shifters don't quite line up. I know as I went down this route. You can get pod mounts that work and as it happens I have a spare set as I recently got myself some x-lite versions. So if you fancy some nos magura style mounts for £10 posted, drop me a pm. It will be cheaper than stx stripping and will work without fettling.