Can Robocopy ensure file integrity?
One large monolithic file will likely cause problems if it fails partway through or if /Z is used it might take too long to transfer.
I would suggest using an archive utility to both split it into multiple files and provide an extra layer of integrity checking of the assembled file. On newer versions of Windows it also lets you use the /MT which transfers multiple files at once which can speed things up on slow links if you also using /Z. So split, robocopy the parts over and then reassemble.