I have done a strat with the full-size Wald buffer (crazy tight, the mini has got to be easier), and yes, using 4 vibrato springs you can fit the battery in between, but the cover stays off. I screwed the springs so tight that the trem blocked itself against the body and then set the saddles accordingly.
"There, in huge black letters, was 'The Grateful Dead'. It just... cancelled my mind out."-Garcia