Brewery SNAFU

There was a total SNAFU in the brewery Saturday night. I brewed an Imperial Stout with a target gravity of 1.080. I missed the mark by a million miles, and came out at around 1.055. My mill efficiency is still crap. Ray suggested .060 which is the space he has his mill set. I have been using .055. This has resulted in around 55% efficiency. I'm going to dial back and plan on using a spacing between .040 -.050 for the next brew. With any luck this will improve my extract efficiency. At any rate I am considering investing in a larger mash tun for future brews in order to meet my high gravity needs.
I'm now planning on making an0ther stout to blend with this one in order to make it drinkable. Back to the drawing board.