Agree, if the bike does 50 to 60 mph, approx 80 to 100 kmh, uphill too, without struggling, or vibrating too much, and some extra speed is still available when needed, all is well. At least on my bike the vibrations at over 70 mph\110 kmh are quite scary, and acts as a very effective mental throttle & rpm limiter! I have a 20 tooth gear sprocket (+1), makes the cruising speed rpm\vibrations more relaxed, at the cost of some acceleration. Anyway the brakes & roadholding is not safe enough for high speed. And why put too much load & pressure on the nice old machinery? If I want to go fast & have more brakes & roadholding I'd ride my Triumph 900. Or my car

Regards
Erling