I wouldn't put a coil in a Trance X, they're designed for an air shock & IMO it'd be horrible to ride with a coil. Having ridden loads of Maestro bikes & worked on them since they came out, I feel they need the rising rate of the air to make it work properly.
I know the likes of the Reign X, Faith, Glory etc. have coil shocks, but they're designed for it, the Trance X isn't. You may also struggle for seat tube clearance, but not 100% sure.