I've had it with this 904, about to give up!

Whoa hold on a second. The kit doesn't come with a new accumulator spring. It comes with two low/reverse springs. You need to reuse the accumulator spring and it goes between the vb and the accumulator piston. If you put the stiff heavy wound spring in the low side then maybe the rear band can't overcome spring and grip the drum. Could this be why?

Craig