Do I need to add extra drivers and countries to my cover?
The named driver and all additional drivers included on your customer's rental agreement are covered by their policy purchased on RentalCover. There is no need to add any additional drivers to their policy because they are automatically covered free of charge. Encourage them to make sure the named driver's name on their rental agreement matches the name on their policy purchased on RentalCover.
US CDI covers Canada, as does SLI (except if driven from New York), as long as the rental vehicle agreement permits it.
They don't need to inform RentalCover of additional drivers or countries they are visiting but there may be territorial limitations within the RentalCover policy, for instance they would not be permitted to drive in countries that are sanctioned by the relevant country regulator.