In my Omega I shoot almost exclusively the .429/240 and .452/300 Speer Deep Curl HP bullets with green or black Harvester Crush Rib Sabots. This is pretty close to the XTP which I've also shot quite a bit. The regular green or black sabots may work fine with you, they may be pretty tight.

I started at 80 grains and worked up, settling on 110 grains of BH 209 for both bullets. Type of primer, CCIMag or Rem STS, did not seem to matter.