I just came back from our USRA Giant Scale races in Illinois...
You guys got anything that will break 245 MPH ?
Fred French flew a 31 lb NA50 powered by an Aerrow 200 twin...I saw 245 mph on radar at the end of the 1600 foot straightaway...
I don't know of anything faster with a propellor....
I think the prop was a 21x25 carbon fiber, rpm around 10,000....