I have the 15000 but I use a loan 350E from my instructor when I go to my embroidery group. I use the same 2GB USB on both machines.
When I first used it on the 350E it created a folder EmbF5. I now put the 350E designs in that folder and the 15000 ones outside of it. It works fine for me.
"Life may not be the party we hoped for, but while we're here we should dance". Anon