As planned, I did my efficiency experiment this past weekend and I think I found my culprits. I double milled my malts to ensure a good crush. I mashed with 1.5 qts/lb. I ran off my first runnings and measured them so I could hit my sparge water volume perfectly. I got my pre-boil volume perfect. I boiled for an hour, and added hops on schedule and lost exactly 1 gallon to boil off which is what I wanted. I hit 80% efficiency (measured pre and post boil).
When I went to fill the conical... not even enough volume to register on my measurements (which start at 4.5 gallons.) I topped it up with a measured 1 gallon of water to see where I was at, and hit 5 gallons on the nose. I lost 1.5 gallons of wort to my hops and kettle! I had been chatting with Denny Conn about my issues as well and he said that he figures about 12oz of beer lost to 1oz of hops. I had 7.5 oz of hops (5.5 whole, 2 pellet) and that would give me roughly 3/4 of a gallon lost to hops, and 3/4 gal lost to keggle pick up tube. That brought my efficiency down to 60%.
After all the experiment, I was able to plug all my numbers into a spread sheet I made and should be able to now, input desired wort volume in fermenter, oz of hops, # of grain, and length of boil, and it will tell me how much strike water I need and how much sparge water I need to get my pre boil volume and post boil volume and fermenter volume accounting for MLT losses, boil off, hop absorption, and kettle losses.
I also removed my pick up tube, bent it down further, and cut it shorter so it now sits just shy of the lowest part of the keggle, and leaves a mere cup of wort instead of 3/4 of a gallon.
If I got it all right, then I should be able to calculate my recipe to 80% efficiency for a batch size of whatever volume I want in the fermenter plus the estimated volume of wort absorbed by my hops, and have an even consistency across the board.
And as an added bonus, I just updated the spread sheet again to calculate OG based on desired fermenter volume at 80% efficiency when I input grains and weights. This will also automatically figure my total grain weight and figure my strike and sparge water volumes. I also set it to calculate SRM as well. I added a sheet for calculating IBUs based on hop type, minutes in boil, and AA, and auto calculate my hop weights as well and input them into the system to adjust volumes to account for hop weights.