I figured that :)
I think Mark's 2x4bbl will be fine at 12.5
There is a lot going on there (at idle) that could be tested and trialed.
My recollection (it could be wrong) was that 12" Hg in drive is pretty decent with the cam etc.
On the other hand, I'd love to see less rpm drop.
Anyway that's its own rabbit hole - although not entirely seperate from what happens in the transistion circuit.