FTPing file from the iSeries to a mainframe

I have a database file with one variable length field in it. The field
is 4500 bytes long plus 2 bytes to contain the field length.

I'm having a heck of a time getting a file to the mainframe as a dataset
with variable length records. I've experimented quite a bit but I keep
ending up with either
1. junk at the beginning of the record or 
2. the records are wrapping or
3. the records get truncated.

My theory is that if I convert the file to an IFS ASCII file and then
FTP it from the IFS, it ought to work, but it doesn't.

Does anyone have any experience getting an iSeries database file with
variable length fields transferred successfully to a mainframe dataset
with variable length records using FTP? If so, what FTP parms did you
use?

Thanks,
Trent Douthat