Given that it's a copy device a FW800 interface for the interface with source devices is probably overkill, it won't be writing to the drives at that speed.
The removable drives will support USB2 and eSATA, and at this stage FW400. A new chipset may become available for them to offer FW800 support (and maybe USB3 when it actually exists, but that's at least 18 months off realistically).
Our official recommendation would be to sync the device to your network storage using the gigabit ethernet and our supplied sync software, or to use one of the drive cartridges connected via eSATA or USB2 (with our supplied sync software, or another mehtod).
The eSATA interface on the SolidStore will be a standard one but ideally we (or someone else perhaps) will make available a eSATA to RED SATA adaptror, although I suspect power in that case will have to be supplied by the RED Drive powerpack.