Thanks Mike, MT60 yup.
Heavy braking potential just isn't something you get with a sls Matchless-wheeled P11, so no worries there! But the tyres fit easily on the rims and between forks and s/arm (with the correct guards), no worries there either - and I have found them better than what I had before.
Not a rational choice for an A though I don't think, except maybe on the Spitfire Scrambler types.
(With security bolts in this case!) But most rims aren't drilled for them are they? Maybe they all should be . . . .?