> Would you agree with that?

I would not. In my view the current TransverseMercator is of almost no practical use because of its fixed parameters. I appreciate this is far from perfect, but it makes it usable. If we hard code the globe, the OSGB and OSNI cannot inherit from TransverseMercator (or only one can :scream:) and we are almost back to where we were - i.e. I can't plot my data (it's on a tmerc grid with a ```Globe(datum='OSGB36', ellipse='airy')``` globe). Does your logic apply to the other projections that take a globe and have hard coded limits or is this a peculiarity of the TransverseMercator?