Alan,
Did you ever get a solution for this one, either from Oracle Support or somewhere else?
I know that OTM uses the finj FTPClient library, but I don't know if it provides a way to modify the parameters which are passed to it. Searching through the OTM property files, I wasn't able to find a solution.
API info for finj is available here:
finj: FTP Client for Java Apps 1.1.1 API
--Chris