Gutsy move! Good work!
Well you don't want more than 15.4v ever to stay inside the fridge controls limit, so it looks like you have some weird choices, but not impossible.
Set it higher so it does whatever it gets to for that 15 minutes while you have the fridge off for that 15 minutes and not need the inverter (won't run at over 15) and then get the steady state to be 14.x as high as you can. (14.8 being ideal but not compulsory.)
Once you get to 90% or so where amps are down, swap over to your finish charger that has low amps but high voltage and carry on from there if your PM's new Vabs is lower than you like. Or else just leave the PM run at the voltage you got it to do after the 15 min is up.
Very interesting! The Paramode converter also had a little pot like that and when it was jacked up it changed both its voltages higher too. Rising tide floats all boats kind of thing.
