At speeds approaching 115 mph some of our senior entrants just couldn't keep up physically with the pace.
I have no problem with limiting the event to a single engine, but want to fuss about the reason given.
There's not a Clown Racer in the world that will run "At speeds approaching 115 mph" unless 100mph is within your definition of "approaching". If there are, they have been well hidden, or whoever was running the clock only timed for seven laps. (Timing for models on 52' lines is for 8 laps, or for 10 if you're flying F2C.)
18 seconds for 8 laps is right at the fastest they will go. That's 100mph. I pit one of those on a regular basis. And it wins "real" Clown Race quite frequently. And ALWAYS gets beat when the pitman screws it up!

Regards,
Bill Lee