I'd say that you would be on the right track by scaling down a quickie for your event. An ordinary quickie with a good sport .25 engine is good for about 90 mph with a prop in the 8-5 to 8-6 range. I don't like standard quickies with only .25 power because they are difficult to launch successfully if the wind conditons are not straight down the runway, due to being slightly underpowered. We ran an event like that in California for about 3 years before everyone decided that the attrition was just too high, and it switched over to low cost .40's.

A few years earlier, my club decided to build a quickie class around a .25 engine with a 300 ^2 wing and a weight of 2 1/2 lbs. Although these flew quite well, they landed like a Formula One and many were destroyed landing by the average flyier.

So if you build a quickie style airframe with 350^2, it should easily reach your goal of exceeding 100 mph, though I would recommend you design it with 400 ^2 to lower landing speeds (it will still exceed your goal of 100). Landing mishaps take out about as many racing airplanes as midairs.

Be sure to experiment with the prop sizes. A .25 sized sport engine will run very well on a 7-6 prop with good rpm if the airframe is clean enough to hook up with the smaller diameter.