I've played that SCGC at Elderly's a few times. I really enjoyed the sound of it but you are right about the set-up.

I know that somewhere there is a site (maybe Frank Ford's) where there is a chart that does a guage/tension comparison. What I wonder is, other than all the set-up considerations that mooh wisely pointed out, the one set-up consederation I maybe wouldn't sweat too much is whether a guitar that is recommentded for medium or lighter guage strings could take the heavier guages once the lowered tensions of C tunings is considered.

...aren't some Celtic tunings so low that only cats can hear them?