Messerschmitt.....if you plan on eventually getting your event to be large enough to garner regional attendance and get spotlights in some of the major R/C mags, you'll need to avoid the time frames occupied by already established scale events. Anything too close to another larger event, and sponsorship is harder to get. Your Sept 14th time frame is real close to Warbirds over the Rockies which is Sept 26th-29th. This is already one of larger shows during the year and is covered by Fly RC, Model Airplanes News, etc and is well sponsored. A lot of big name pilots go to the big events(like Mac Hodges B-29, Dino Digornio and his scale award winning planes, etc) and thats how you get audience attendence(if your looking for that anyhow).

Im not telling you when to hold your event, you simply asked if there was other events already in that general time frame.