Makes sense. Thats why I have forced ext air.
It get away from a hot rated expensive alt.
And I have a 3GM capable of second alt but whats the point, battery dictates acceptance.
Once you have spare current capacity no point. ie over the 85% shoulder part of curve.
A stash of belts green stripes, a quality auto ext regulated spare alt & i'm good at this stage.
Custom belt tensioner I fabbed.
Although I suspect IT is right. But my whole setup cost a third of a Balmar.
Strictly DIY tho, cant see a pro staking their reputation on it.
4.5 hours motoring from barrier from 12.4V got me to 6A tail current.
Batteries at 12.83V rested 48hrs later.