Richard, thanks for taking the time to respond, very much appreciated, your fair mindedness was never in doubt..
I wonder how many if any who retro fitted multi-pot callipers to their Morgans, or any other car, even contemplated fitting an alternative master cylinder...?
I on the other hand would have done, as the result of fitting a new master cylinder to a Mk1 Ford Escort, many years ago, when according to the part number the cylinder supplied was the correct part for the year of manufacture, but the brake pedal travel was discovered to be excessive after I fitted it...? With a bit of investigation I found that Ford had changed the bore of the master cylinder mid year and I had been supplied with the wrong part, which looked very similar.
If designing a multi-pot calliper for the aftermarket it may just be a consideration to ensure that the overall fluid displacement required is similar to that of the original larger cylinders, or perhaps just a tad more, thinking that a little bit more pedal travel might be acceptable... Other than that, selling multi-pot callipers to the home mechanic/enthusiast which also required the expense of upgrading to a matched master cylinder, could cause folk to think of reassessing the initial purchase decision, and risk reducing sales of the calliper..?
As ever just thinking in type.
