I had a similar issue,

In the end i upgraded the Sena to a 30k,

However that is not without issues.

You can do

Nav 6 to Sena as headset (bluutooth )

Phone to nav 6 as phone

It works, but you loose phone voice commands once the nav is switched off

This method worked better


Nav 6 to Sena ...

I spotted this on another forum, whilst searching for a nav6 fix

A hack to use the Honda handlebar remote with the 550

Had i not sold my 550 i'd be having a go at this

https://www.st-owners.com/forums/thread ... ut.131637/

hth
Santa