If you reduce grain, and keep the eff. you arent solving the problem.
The issue is that I need to reduce my lauter eff., reducing the grain bill will not do this. Reducing my sparge volume will. On my next brew I have almost 8 gallons pre-boil, the sparge will contribute only 3 gallons.
My lauter eff. is pushing 91%, I need to back that off so that I can maintain wort quality.
Since the grain is the buffer for the pH during the sparge, I am working up numbers for the % of pre-boil wort that should be derived from sparging. Obviously this will be tied to the size of the grain bill. More grain, more sparge water, less grain, less sparging.
The way people brew now, if you ALWAYS use the same qt/lb mash ratio, the smaller your grain bill, the MORE you sparge (to reach your boil volume) which is counter productive when trying to avoid tannin extraction.