Small correction, the stroke is in fact 30mm (28mm standard + 2mm) and bore 36mm, comes with a stuffed crank.
This makes the Rovan the same capacity as the DLE30 but being a piston ported (as opposed to reed valve) it can rev higher with the correct port timing.
18x8 prop should be small enough to get high rpm out of this engine, not sure about the vibration level but this engine can rev very high on cars.