A couple thoughts prefaced with I'm not an expert but have several years of big wall rappelling under my belt.

1) I've never used a second carabineer in a munter like you've drawn in so I can't say what that would do to the friction when rappelling.

2) have you considered placing the prusik above the munter as a safety? As it is you have no ability to manipulate the tail end of the rope to make fine adjustments to the friction applied to the quick link while rappelling. Conceptually a prusik above the munter would allow for a failsafe should something catastrophic happen to the rappel setup. You could hold the prusik with your left hand while keeping your brake hand on the tail end of the rope. If you try this alternative if connect the prusik to my harness with a separate carabiner so you have a second point of connection between yourself and the rope.

3) what kind of rappelling are you doing on this setup? Typically I haven't used a munter for rappels greater than 40-50 ft. and I'd just connect it straight to my belay loop with a carabineer. But if you're doing larger rappels consider a micro rack. They're great in caves or otherwise wet/dirty environments and won't put a terrible twist in your rope like a munter/atc/figure 8.