I would run 25:1 (40ml per L) in both. Depending on the age (I remember you saying about a rubber snorkel so I would say pre 1976 on the mayfair?)
The reason being that many of these engines have bushings instead of roller bearings (especially on the little end).
40:1 is pushing it, but I doubt you would have done any damage unless it is being run full throttle through 2ft high grass day in day out.
The oil you are using is of decent enough quality, so don't worry about carbon build up.
