Thanks for the link - tis a convoluted area for sure.
Looking at that site, and reading the comments I'll try one size down next, EG the 27 x 1 1/8 tires. As I don't think I'll need new tubes, and my rims are 27x1, so I'm worried 27x1 tires would be to narrow for the rim. The bikes primarily going to be used for pleasure rides and commuting, so comfort is a bit of an issue also.
To answer that question, the moto has vertical dropouts, with not a lot of room for play. I seat the tire at the inside end of the dropouts.