I think the screws are 3/4". Regarding the horns, I threw the Sullivans out and used Rocket City #10 Pull-Pull horns. I used the Sullivans in a H9 Cap and the DP Ultimate. I just don't think they're that great. If you want to use Horns I recommend the Dubro Large scale. BTW, I just finished, well almost finished, my Edge. It came out WAY nose heavy - had I known this I would have used the elevator servos instead of the pull pull.