I actually think the F5U was a good concept. However, they should have made it into a bomber instead of a fighter. The proto fighter version was capable of 430 mph speed using two 1350hp P&W R-2000-7 engines, with the fixed landing gear shown above. Further testing revealed a top speed of 504 mph.
I have my doubts about this design as a fighter, I just don't see how it could roll sufficiently well to dogfight, though it might have made a good bomber interceptor. It could carry 2000 lbs of bombs in the fighter configuration. Scaled up and given either 2 or 4 P&W R2800 engines, it would have made a very fast bomber with a significant payload. And it could take off from very short runways!
No, those are P&W radials, but no prop. There's a driveshaft that goes to the outside and drives the props at the outer edges. This design provides about 20% better cooling flow over the radial than having the prop directly mounted on the crankshaft.