I've successfully used 32GB flash drives with Poseidon & RapidRoad. Think the stack overhead was... *maybe* 2MB? I could go back and check it, if that would be helpful. Also plugged in a 4TB drive once. It recognized that it was plugged in, but was unable to read due to the drive being formatted NTFS (and I didn't have an NTFS file system installed at the time), lol.
In any case, agree with the above comments - 64GB USB flash drives can be purchased new for under $20 USD. Get a couple of those, one to keep as a backup, and you should be good to go.
