I've got the 1/7 DM-1, which is probably quite a bit heavier than your IGT2.. I've tried a couple .21's in it, and I just feel like due to the weight and gearing, it needs a .28 to muscle it up to top speed sooner. I have a new Fire 11 sitting here, and have considered trying it in the DM-1. But even as powerful as the Fire 11 is meant to be, I still wonder if it would have the mid-range grunt to push my DM-1 the way it needs to be..