Those mph numbers are taken with a Bushnell radar gun.
We checked the gun against a police radar gun and came up with the same mph, so the gun seems to be accurate.
The mph speeds shown with the 26cc were 6 up wind speeds of 79 mph and 6 down wind speeds of 91 mph.
Split the differance it is about 85 mph, I went conservitive and said 82 mph.
The best out of a dive, down wind run I got was 116 mph ( just for giggles )
By the way plane is a Seagull Laser 200 ( 11 lbs. 2 oz. ) since you were talking about drag issues.