Welcome Dan!
The developer tool that will really help you here is the Browser tab (on the left). It breaks the MEM_FORMAT into a tree you can browse, so you can confirm Chirp is parsing your struct correctly and the bit ordering is correct. Thanks to Dan for this very useful tool.
I agree, the browser tab is you friend ;) Let me add that you can make changes and try them with out the need of a full development environment using File - Load module which load a py radio module at runtime.
My only request now is that if someone is already working on adding FT-60 settings, stop me now so I don't waste my time.
Starting a feature request, assigning it to yourself, and setting "In Progress" would prevent anyone else from unknowingly working on this task.
I had my ft60 back after long time, here I am if you need a some help or perhaps a beta tester.
73 de IZ3GME Marco