Transferring Unicode data

What is the "safest" way to do file transfers with Unicode data? Meaning, to keep the integrity of the data, not from a security standpoint.

I need to transfer multi-language files between outside sources (to and from the system), e.g. Excel, or other PC file and the IFS or a native *FILE. I have tried various methods, but along the way some data gets garbled. Example:
- In Excel, I saved it as Unicode text.
- Drag and drop from the PC to the IFS via Navigator.
- CPYFRMIMPF to a DB. DDS Definition:

COL1 40G CCSID(13488 20)
COL2 40G CCSID(13488 20)
LONGFIELD 2000G CCSID(13488 1000)

- Reverse the steps to bring back to the PC.

The result is:
COL1 contains the data, but has a leading x'25' in all the records, except the first, which had a bunch of x'33' characters, instead of real data.

COL2 seems to be OK.

LONGFIELD gets a bit garbled, but not completely.

COL1 and COL2 only contain numbers and some basic punctuation, like a '-', so it might be coincidence that the data is OK there.

Since there are several steps happening during the transfer and I can't display the representative characters on a 5250 style session (those languages are not loaded on the system), it's tough to debug this.

-mark