Nice one Jerry, that's a good bit of research. All we need now is a place where we can buy these tyres at a reasonable price, otherwise it will be an expensive experiment, as you say.
I suspect that a 195 would fit the 7" rim quite easily, a 185 would be very difficult, but possible and anything smaller probably wouldn't get on the rim at all. It doesn't seem that anyone has actually used this combination yet though. I've currently got some 205/50/16 Yoko 032's on the rims, and can confirm that the 50 section will fit under the wheel arches of a 21, but on a Seven, I can only say that they look good, but are VERY tight under the front cycle wings, although I may be using the smaller wings, which would bring its' own problems 😳
Jack, nice to hear from you, I understand that Emilly was involved in a little Anglo/French misundertanding recently. How are things now? BTW, have you had any luck repairing my printed circuit board yet?
Now with a working Seven, practically ready for SVA.