Add additional keyring to an already encrypted file

Hey,I'm working on allowing the encryption of files up to 25GB up from of our current max of 20MB. In the current implementation we  allow the addition of optional PGPPublicKeyRings after the file has already been encrypted. Untill now we would just re-encrypt the file with all keys including the new optional keys. But with the increased filesize the current solution of re-encrypting every time would be very time consuming.Is there any way to simply add an additional PGPPublicKeyRing given that you have all the data to decrypt the file?Regards,Steffen van Kilsdonk