I grew up at the northern end of 127 near Bryan.

Tandems don't really have different pressure requirements, only that they are carrying a lot more weight, so you need to have enough air to keep from getting a pinch flat. 50 psi seems a little low for a 27x1 1/4. I would keep it around 70.

French bikes up until the mid 1980s used their own standards for almost everything. Here is an article that covers the differences. French Bicycles