I played like that with my Mini all last year. I used the APP 50 round scope hopper and a Guerrilla Air 13/3000. I loved it. I really wish you could flip the reg around though. Now I just have to find one of the snub nose Freak barrel fronts and I can run with the shorter barrel. I only had to shake a few times but I did get caught without a round in the chamber once or twice when I really needed it... I haven't resorted to making my own 100 or 50 round hopper agitating yet, though I should.
My efficiency sucked as well, I was lucky if I got 100+ shots out of the 3K (Yes, filled to 3K). Probably need some tweaking or the new poppet since I got one of the dusty boxed mini's from the top shelf in my local shop (V1.1 board). I play woodsball with it by the way.
Love the mirco mini though. You can move so fast and pop up pretty darn quick when you need to.