I was looking at the 120s in both NBT and Sierra Pro Hunter. I found this recoil calculator and figure I can push the 120s at 2600 out of the 7'08 and have similar recoil to the 243 pushing 100s at 2900. I think I'm gonna go 7'08 for his first centerfire.
http://www.handloads.com/calc/recoil.asp