I have observed three possible problems (FSX Limitations?) in the Radio Stack...
1) The DME: when placed in "Remote" mode, the KN62 will display Distance/GS/TTS info whether or not the KX155A (i.e. NAV1) is on or off. One can shut all the radios off, Turn on Nav/Comm 1, select a station in Nav1, turn the KX155A off, then turn on the KX62A and place it in Remote mode... the DME info (Distance etc.) will display correctly.
2) Regarding the KX155A, unable to use the following feature:
"Depressing the NAV frequency transfer button for 2 seconds or more will cause the display to go in to the ACTIVE ENTRY mode. Only the ACTIVE frequency will be displayed and it can be directly changed by using the NAV inc/dec knobs." (p. 33, Silver Crown Plus Pilot’s Guide)
"Only the ACTIVE frequency will be displayed" does work when the NAV frequency transfer button is depressed, however, when attempting to "directly change the ACTIVE frequency" it is the STANDBY frequency that actually changes (which can be seen once pressing the NAV frequency transfer button).
3) Regarding the KR87 (similarly to the KX155A above) unable to use the following feature:
"While FLT or ET is displayed the “in use” frequency on the left side of the window may be changed, by using the frequency select knobs, without any effect on the stored standby frequency or the other modes." (p. 44, Silver Crown Plus Pilot’s Guide)
Again, similar to the KX155A, in this case with ET or FLT displayed, using the frequency select knobs only changes the STANDBY frequency (which is not seen directly until after punching the FRQ button -- can be observed changing in the 'Tool Tip' box).
The above items just a "fwiw"... very minor imo, but thought I would mention them.
I should take the time here to mention my sincere appreciation for all the Radio coding work, as it was
to see such things as the ET Count-Down timer enabled in the KR87 -- also e.g. the KX155A NAV "ACTIVE/CDI format", the "ACTIVE/BEARING format" etc.
Looking good regards!