May I add to this thread?
I'm trying to do something very similar and also with Auria as the subject. Auria semi-supports MMC (but not completely) so HUI is the only reliable way to remotely control its transport controls. Following a load of confusing research into the HUI protocol, I've been experimenting with trying to send some HUI SysEx strings to Auria from MidiDesigner and I've hit a problem.
What's happening is that MD appears to insist on modifying the strings after I've typed them in. For example, I reckon that to tell Auria to PLAY, I need to send the SysEx "F0 00 00 06 05 00 B0 77 7F F7" so, ignoring the first F0 and last F7, I type "00 00 06 05 00 B0 77 7F" in to SysEx properties field and apply it. However, MD has actually saved it as "00 00 06 05 00 7F 77 7F " so it doesn't work as intended!
Now, it may be that my research is no good and what I'm trying to send is rubbish anyway but that's not the point. Why is it that MD is modifying what I've entered?
Please help - this is making me tear out my hair! ;)