I'm a moderately experienced all grain brewer with about 15 batches under my belt. I recently acquired a larger brew kettle and was thinking about scaling up my batches to 8-10 gallons and splitting between two carboys. I currently have a 5 1/2 gallon mash tun which works great for 6 gallon batches with 11-13 lbs of grain mashing at 1.5 qt/lb. My question is this:
Would I be able to achieve decent efficiency if I were to mash, say, 18-20 lbs of grain TWICE at a thickness of approximately 0.8 - 0.9 qt/lb before sparging? It seems like this would be a way to avoid mashing two different groups of grains in my smallish mash tun. I know people use this method to make different strength beers with their first and second runnings (traditional partigyle), but I was thinking of just combining two runnings to make a larger volume of wort. I understand mash thinkness can affect the body of the beer and efficiency of the mash, but was hoping to get others thoughts?