When I use BIAB I get different grain absorption rates with different grain bills. For instance wheat doesn't absorb much at all. In order to try and have consistency with my process, I decided to not guess my absorption rate and just stick with 4.5 gallons pre mash every time.
I told this to my LHBS (great guy) and he said instead I should try to focus on getting the same amount volume of pre boil and post boil liquid. He says this would be a better thing to tighten up my process. But seeing as I am having a hard time doing that, I don't know what I should do.
Can I get some thoughts and advice on this? By the way I usually get around 80% efficiency.