Mash Boil, Sparge Absorption (MBSA)

I have a simple 2-vessel (mash tun + kettle) HERMS, I prefer to no-sparge or minimize sparge volume as its just another step (I collect water from my kettle/heating vessel when draining and then pour it in the mash after the wort's pumped out). Anyhow - I spent a while digesting BrauKeiser's batch-sparge model/analysis and come up with this SUPER simple rule of thumb that achieves all my main goals while being easy to remember and implement:

The Rule:
"Mash with your boil volume, batch sparge with as much water as your grain absorbs" or MBSA "Mash Boil, Sparge Absorption"

There's a few interesting caveats here:

1. this works to produce worts up to 1.1 OG, after that the mash will get thicker than 1.2 qt./lb.

2. if you're sizing this process to your mash tun (to understand your maximum) you'll find that the amount of sparge water may require more than 1 batch - this is actually very elegant as it will require a # of batch sparges that keep efficiency close to 75% without you have to do complicated calculations to hit a consistent efficiency.

I know there's a lot of assumptions here and that efficiency tends to drop as the beer gets bigger, but each time I do the math for different scenarios its surprising how close it works out. Plug it into BrauKeisers analysis/formulas... it's amazing how well it works out!

I didn't mention clearly that one of my primary goals was that conversion efficiency stay consistent and in a healthy range no matter the size of the beer. I understand efficiency goes down with higher gravity, and that's ok - my point in caveat#2 is that if you have appropriately sized mash-tun and kettle then you will find that you tend to have to do multiple sparges when the gravity increases which tends to balance out the loss in efficiency ... magically...

(I use 15 gallon mash tun, do 10 gallon batches - maybe that's just a sweet spot?)