Already doing that, but a great idea. One of my bow friends suggested I do that, so on my last 3D shoot I shot with my loaded backpack, hunting clothes, arrows in quiver, plus a belt/leg quiver, etc. Luckily my form doesn't contain a fore-arm slap component. Haven't had the string ever hit my forearm, even in my big jacket.

No point of impact change with a full or empty quiver. Haven't tried without the quiver attached though.