I'm using a JP free float hand guard and the Precision Reflex gas block will fit and I can even access the gas adjustment screw easily through the slots on the handguard. I know this because it has a .936" under the rail already. I just bought this rifle from a local guy instead of building one myself because he used all premium parts (except for the trigger) and I bought it for less than the sum of the parts. Problem is, for whatever reason, he put the .936" gas block on the .875" barrel and just snugged it up with the set screws. My bad for not checking it closer before buying it I suppose. He marred the barrel up pretty good too by overtightening the set screws to compensate for using the wrong size. Crap!
Having said all that, I just looked at the SLR that Warthog suggested and really like the way it's designed. I like the idea of being able to shut the gas port to the fully closed position while cleaning and then being able to open it back to the exact same spot. Too bad they cost $55 more than the Precision Reflex, but I'm going with the SLR anyway.
Thanks to everyone who posted here, I really appreciate the feedback.