I think it sounds like a decent idea. Keep in mind you will have no control over the sizes and shapes of the rock that you will receive but if you are handy with a hammer, you will be able to break down bigger and chunkier pieces. The two day shipping is not horrible plus you will have an empty new tank to cycle the rock. BTW, is the rock cured or not cured? Judging by the price I would guess not cured so that pretty much solves your problem right there! The two day shipping is neligible when the rock isn't cured in the first place. You will have time and opportunity to let it cycle through on its own.