>If you would just try CopyFile function to copy the file as is, would it work?

That was the answer, Naomi. I always knew the collective intelligence on here was lots better than my own feeble brain. Thanks for the nudge in the right direction.

So apparently Fox is doing some fairly intensive two-way communications internally in the COPY TO TYPE XL5 format conversion that slows everything down dramatically when it goes across the Internet.

Doing it locally to a server temp folder then using COPY FILE to transfer that to the user-selected destination took only a few seconds with a much larger file than I had tested before.