I would never suggest that you not shoot sabots from a 1-48 twist barrel. I've had good luck with them in several of my guns with that rate twist. I think you should shoot patched round balls, conicals and different sabot/bullet combinations and let the gun decide what it likes the best. Don't forget to try different powders too. You'll get different results from each type.
The 1-48 twist is what I feel a generic twist. I've had good results with it, but not the best!
It's best to decide up front what projectile you want to shoot and then narrow down your choices from there.
The T/C Firestorm is one rifle I'd like to have, but in the 209 version. It has a faster rate of twist barrel...1-28" This is the favored rate of twist for the sabot shooter in a 50cal. rifle.