Thanks, Dan. I will look at forcing the "off". (As a newbie Ham, it did not even occur to me that "duplex==off" must meand "TX disabled".) I will run the tests and see what happens, and patch the test code to make it work. I think you will want to review any changes I make to the test code very carefully before accepting them.
With respect to the MARS/CAP mod: It appears that this basically turns the FT-4XR or FT-4 XE into the "Asian" version, which in effect removes the regulatory restriction and lets you use the radio's entire UHF and VHF capability. A user could then select the "Asian" version if they mod the radio.
That was going to be my next question. I propose to add two new radios: FT-4XE and FT-4(Asian).
Since I don't understand the aliasing scheme, I intended to subclass the FT-4 class and modify only the frequencies (and the step size), so the number of lines of code is truly tiny. However, this will add these radio names to the list of Yaesu radios as full top-level peers, not aliases or something. Is this acceptable?