Phil raced the bike at Philip Island in 2018. He won the class due to a DNF by David Woolsey in Race 4. His fastest lap was a 1:58.005. That's over 10.5 seconds slower than the lap record, and 8 seconds slower than the 39hp production machine mentioned above. No disrespect to Phil at all, but this is what happened. The competition was not there.Greg Brillus's Twin racer also won Philips Island with Phil canning aboard.
To put things in perspective, my 2nd ever outing on any motorsport circuit was at Philip Island in 2016. I did a 2:01 with a top speed of 183kph on a learner's approved cbr250r proddy. I was about 95kg plus leathers, helmet etc at the time. The Vincent twin achieved 212kph in 2018. 29kph (18mph) faster than me, a tonne more hp and only 3 seconds quicker??? And I'm only a wood duck on a good day. The only way of knowing what a motorcycle is capable of is with a good rider onboard.
I've been fortunate enough to ride both of Luis Gallur's 500 Eglis in 2018. One which Cam raced at the IOM and the other which Maria Costello was racing here in Australia. Luis told me Cam's bike had 53hp and Maria's had 48hp. Luis wanted more. 2 weeks earlier Cam did 1:49s at Eastern Creek and had the pace to win the class if he didn't have 2 DNFs. So why bother chasing more hp? Are you better off with a time bomb or a reliable race bike?
Ben Kingham and Josh Brookes are a great example. From what I understand there was nothing particularly special with the engine. Smoothness and consistency resulted in quick lap times. I don't think they were the fastest in a straight line either.