I normally brew 25Lts. 
I scaled up a recipe in Promash & what I was aiming for was an ordenary English bitter of approx OG1042. What suprised me is that i only sparged 10Lts more than I usually do stopping at 1010 so as not to extract tannins etc, at this point I had collected 40 Lts @ 1070 so I had to add 18 Lts of treated water to acheive a pre boil target ov 58 Lts.for a 90 minute boil. My oryginal calculations were based on an efficiency of 75%. Is it normal to sparge with less water when brewing larger quantities? i also ended up with a higher OG to what i was aiming for. is my efficiency higher than i estimated or is this to be expected with a larger brew length? One other thing, for this brew unusually for me I did a protein rest @ 55C for 30 munutes prior to 75 minutes @ 66C. cheers
Marc