Thanks! The inside of the motor mount is roughly 40mm so there is quite a bit of wiggle room. I recall I tried to stuff the 1515 motor in it, I think the only reason why it wouldn't go in was cause of the fins. I didn't take a photo of the clearance but this outrunner has a 36.4mm diameter...compare this to a 540 motor (36mm diameter):
it's kind of hard to see cause of the lighting but look at the bottom. plenty of room. (: