Rear brake caught on disc 'lip'

[Crimson]

I was wondering, does anyone here have any tips on how to remove the rear brake, which is catching on the slight 'lip' of the brake disc? I can't rock it about to move the calipers apart, because the position of the two holes that fix it to the swingarm don't allow it. I'd rather not bleed the brakes. My plan to leave the hose connected, push out the pistons, clean them up a bit and push them back in with, if necessary, new pads.

Thanks