I ran 15/39 on my '28 (which I believe was totally 28se) and it was flat out by the Dunlop Bridge.
I ran 15/40 on my mc18 (unknown box, but as it's a dry clutch, probably a '21) and was flat out about 2/3rds of the way along the "straight" between Church and Rocket at Anglesey, swapped the front to a 16 and instantly went 4 seconds a lap faster
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