Just tested with the enclosure I have here, set it up to use the drives as two individual drives and that works too, as they show up as two separate drives once the enclosure is connected to the Almond+.
What I don't know is how well it would work with an enclosure for say 7-8 drives and I'd really suggest running RAID on something like that anyhow.
I also tested to write to both drives at the same time via FTP and that works just fine as well. The performance will of course drop a bit, but again, we still have a fair bit of work to do on the storage side of things so this will hopefully improve.
One thing about USB hubs though, you need to use powered hubs, bus powered hubs won't work.