Ok - I never said the pMag will not advance without a MP connection, I said it will not advance as much. I also said it will not advance more than if connected. Perhaps I could have been more precise.
I did not list all the possible permeations, I just bounded the issue. If the pMag is open to atmosphere it will advance beyond your fixed mag setting with altitude - as you want it to do.
The comment on advance and ROP climb is not applicable to all this. I do caution against reaching for the “timing lever” as the only option for managing CHTs. My experience is for WOT climbs, CHTs are coming down as I’m passing above 7K’ or so as engine power is going down.
I run dual pMags with the jumper in which limits the pMags to a maximum of 9 degrees of advance (so for my current IO-360-M1B this means the most advance will be 34 degrees). Engine Performance is superb across the operating envelope, and far superior to the 400 hours I have flying behind mags (on the RV-10 before the pMag install).
I don’t have any experience with the EI Commander, so have no clue what it (or other similarly add on controllers) do to engine timing. I would not recommend adjusting such a controller to have a maximum timing advance beyond 9 degrees. What I tell other builders is install the pMag as listed in the instructions and fly with jumper in. This is a solid, and I consider conservative approach for 95% of RV pilots.
Carl