Can you use a USB com port on Mac? (I would assume so.)
My Win 7 machine does not have a traditional RS-232 Com Port, I had to purchase a USB Comm port converter.
Then you need the iFly USB to RS-232 cable and a null modem to mate the cables.
I found that setting the NEMA output for 5 transmission per second seemed to satisfy the 720 for smoothness and responsiveness to button pushes and functions.
Do you have an ideal setting in mind for the transmission per second?
5 should work fine...but "3" would more closely represent the actual GPS refresh rate.
I'm not much of a Mac user so forgive my ignorance. But couldn't you just get a USB to Serial converter for your mac?
Greg, how did you set up X-Plane to work with the 720?