Another update from yesterday's second brew, a quad at 1.092 with 2lbs sugar and 16.X lbs grain. I tightened the gap to .035" for this one one after the .040" on the 1.050 brown.
Recirculation was still way better than my Corona crush, and I hit planned 70% efficiency on a bigger beer. The brown ale at average strength got 68-9%, which isn't far off, but I usually lose efficiency on higher gravity beers. This may have partially been due to the 90 minute boil and a little extra water to compensate. FWIW I do a dunk sparge for a few minutes in a 10 gal bucket with some stirring.
The grain feeding was flawless, confirming that it was the re-milling of the first bit as I was dialing in my crush that caused the issue with the brown ale batch.
Re: some of the debate above about gap size, it seems the maltsters supplying pre-crush probably have in mind commercial setups which may vary from a home-brew setup, especially BIAB. I've read that the courser crush that enables better recirculation gives the best efficiency for eBIAB. In the past I've noticed looser crush giving me worse efficiency, and I've had issues with recirc rate. So far the MM3G seems to be giving me better recirc rates and about the same efficiency (maybe better for the quad mash), which at least frees me from babysitting the mash to get other stuff done. The Corona seemed to yield a fairly inconsistent crush--some large/whole, lots of small particles and flour. I may try a bit tighter to see how that works out. I may also try a different 'sparge' manifold for the recirc to see it that helps efficiency or recirc (I currently recirc back into the center of the mash a few inches deep with streams pointing out).
P. S. the whirpool return I also recirc through allows more power to be used in step mashes without bag burning or scorching. Thanks for the idea on that,
@Bobby_M . Thicker mash with a sparge also helps these steps go quicker.