Bill, thanks! I've never flown it on 18mm. It would probably do ok on a Est.C6-3. I may try adapting it down from 24mm one of these days and see how it does. It came out lighter than I expected, but it's pretty draggy. This model would be a great candidate for a interchangeable mount. I thought about doing that several times during the build, and waited to install the mount until very last minute for that very reason. I knew I'd be flying it one 24mm most of the time anyway, so I glued the mount in. I was a little worried about adding weight to the rear also. I knew it would marginal, but I didn't think a D12 would tip the balance so adversely. It's got 1/2 ounce added in the nose now, and that seems to have worked out. C11-3 is a good motor choice. Not super high, around 400-500, and gives it a nice kick off the pad. Oddly, the cluster never crossed my mind. Two Quest C6-5 would probably work out great!