I just finished working up a load for the 124 grain XTP using HS6. 6.4 grs. to 6.8 is Hogdon's listed data. I'm worked up to 6.7 right now and it is very nice, certainly not a standard velocity load. The pressures are very stable, though they are in the higher working range. Above the 124 gr. bullet weight I've gone with Longshot, which has been working with a simular stable yet higher working pressure. Go to Hogdon's loading site for a fairly good list of loads to choose from that utilize IMR, Hogdon, and Winchester powder's.
I don't know what OAL will serve you well with that bullet, but I would think some where around 1.090" would be a good starting point. Take the barrel out of your gun and check to be sure you are not touching the lands at 1.090". If it isn't touching, then you should have a safe starting OAL to work with. It is also important be sure that OAL will cycle in your firearm well. I've found 1.100" to work well in mine.