Well..MonkSeal:It's not about your can light, it's about equipment configuration. DIR way is no right waist D-ring and canister should be ditchable. If you put buckle flap inside you'll have difficulties to open it.
#1: If I put the opening on the inside, I will have no problems opening it. The waist band must be completely undone to ditch, and once it's undone the opening will be free to open.
#2: If the *reason* for having a buckle instead of something else there is to make the canister ditchable weight, then the *reason* disappears when the can is not ditchable weight, therefore the buckle is not needed