I have managed to have Cartographia E32 maps loaded on my Zumo 550.
I have managed to delete the entire North America NT from my Zumo 550.
Cannot get it to re-install as I do not have an un-lock code/whatever.
Well. That was an easy fix. Only took 5 hours of billable time , everybody in the Garmin support and software divisions, and remote operation of my ancient laptop.
Good to go.