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I'm pretty sure that the STH12 (Driver or OS) won't have the same screw pattern as the guardian. However this isn't a huge problem, you will most likely have to mount +/- of where you currently mount. But appart from that there shouldn't be any complications, skis are generally good for 3 mounts.
Hope this helps, if you've got any questions, feel free to pm me, Joey
If the holes lined up or you think there isn't enough distance, you could always go with inserts. Binding Freedom is the original company and Jon is great to order from (he is jondrums on TGR, for reference). I just pulled MFDs off my Caylors and am about to swiss cheese-mount them with inserts for FKS and Dynafit Radicals, so hole spacing shouldn't be an issue for you.