They are the nuts, agree with comment that they're the equal of any cantis.
That's good to know.
I'm thinking of modifying an old small wheeled shopper for use as a runabout; I want something that doesn't take up so much room in the hallway. The things I'm looking at come with old 500A steel rims, 440mm bead seat diameter; alloy rims the same size aren't available and it's virtually impossible to find decent tyres in that size anyway. I was thinking of rebuilding the wheels with modern alloy 20" 406mm bead seat diameter rims, commonly found on BMX bikes and modern folding bikes, so there's plenty of tyre options.
If there's room for fatter tyres, and I think there will be, that will make up for some of the lost wheel diameter, and hopefully be more comfortable over the potholes, but the brake surface will be about 17mm lower and the original brakes are hardly low profile to start with.
It's all still in the pondering stage at the moment, but it might be a fun project if I find a suitable bike at the right price and not at the other end of the country with no postage option - as always seems to be the case with Ebay and Gumtree.