I use the USB-SuperCharger software which considerably speeds up USB drives but unfortunately this is incompatible with DO.
It is too complicated to explain here so you may like to review their website - the version for 2Gb drives is free! easyco.com/usb-sc.htm
When exporting DO only sees the 'base' drive letter and not the mounted drive/partition presumably not understanding it is a USB drive/partition.
It would be rally useful to be able to export DO to this SuperCharged partition as it really is much faster.