Here I go again... answering my own question. But revising it, so there is still a question.
The SftpSshServer won't accept the OpenSSH style public key, rather, it requires an RFC 4716 compliant key. Fortunately it is very easy to modify by hand a single-line rsa OpenSSH key and make it into an RFC 4716 key. This works as long as the OpenSSH key is SSH-2 RSA when burned I would think.
So, my question now is: It looks like ComponentPro lists OpenSSH compatibility, so is there a way to make the Sftp server accept OpenSSH public user keys for authentication? That way I won't have to keep tweaking the OpenSSH style keys people send me.