fliggyg, you should be looking for app. 1/16 inch gap. Those are big hinges. Here are your choices:

#1 Cut a bevel around the hinge slot so the knuckle of the hinge will inset into the balsa for a narrower hinge line.

#2 Use a smaller hinge. They will now be loose in the existing slots due to the thicker ones in there currently, so, gorilla glue is an option as it will fill the void.

#3 Plug the slots with balsa and wood glue, then re-slot for the thinner hinge.

#4 Abandon the slots and cut new ones next to them.

Option #1 is the easiest at this point. Here is a pic of what to shoot for. Good luck. Joe