Alasdair,
Yes, and this is still an item on our todo list. The last word on this was our provider created a couple of prototype TTL to RS232 cable. I could get neither of these cables to work. The issue could be the cable, the TTL port on the iFly, or the OS. We spent a few hours researching this but did not find an easy way to determine the failure point. We did modify the code to allow exposure of the TTL port (you can see this in the new Serial Ports dialog, where you can manually enable ports that were otherwise hard-coded to a disabled/ignored state). But I still don't have a tested working solution to offer you.
As you state, there are only (I think) 2 or 3 of you in this bucket. At this point, between myself my dev team and my hardware provider, I think we've spent more resources than we could ever possibly financially justify. But I really wanted to get this working! But at some point I gotta give up. Have you ever considered upgrading to a 720? If so, give Shane a call...we'll try and make it worth your time. 214-585-0444 x804.
Thanks!
Walter
PS, I'm moving this to the Owners forum.