Adding additional juice partway through fermentation?

I'm making a blend of perry and cider, and decided to play with using heat to reduce and concentrate the batch. I simmered 5.5 gallons of a 50 50 blend for 2.5 hours and reduced it to just under 4 gallons. I am planning to add more per juice to bring the volume up to a full 5 gallons. But..... The pears I'm planning to press I just picked today and have not cold conditioned yet. I am guessing it will be about 5-7 days before they'll be ready. So I'm thinking of starting the fermentation with the current batch and adding I the rest of the pear after pressing next week. Any potential problems of adding more juice partway through the fermentation?
Thanks!

Tanks