Deano :- if your going with any Bob Long, Nif-Naf had it spot on Mate, Use a Low Pressured Reg only,
other Regs out there are around 800 - 600 - 450 by taking out the shims all Vary slightly -25 going on to +25 when on the bottle, however the SLP is a 300 -25 going to +25 so you could be firing your gun at 275 psi going on to 325 ,
Now this is LOW and is the reason if you put a higher output on a Bob Long gun, you will probably blow a few things,
sometimes it works for a few people by putting a high end reg on them but for the most ... it doesn`t.
Your getting a Beauty ?? Keep it that way.