Skipping checksum when grafting files on Object store

Hello. We’d like to publish a large amount of files on S3(compatible) storage using cvmfs via the grafting process. However, we are finding that it is slow to graft since the entire file has to be read in order to produce the checksum. Is there a way to use the md5sum info provided by the S3 storage instead of having to recalculate it?

Thanks in advance!

Myung