Hello
I managed to get my HD T2 to record on a USB stick. The problem is that the HD will not format a USB stick, and therefore it is not usually available for recording.
However, I formatted the stick on a Linux system as ext2, and then put the UUID of the partition into the file /var/lib/humaxtv/ext_hdd_info. On the next reboot, it recognised the USB stick just like a hard disk prepared for recording. It seems to work ok, although the box can be slow to respond - probably the USB stick is a lot slower writing than a hard disk, causing some delays.
Please don't ask me how to find out the UUID without Linux - although there is probably a way to read it from the HD itself.