I just made one similar to this one http://www.homebrewtalk.com/f36/lets...ne-mash-74927/
. I made a 10 gallon batch which turned out to be 12 Gallon. I think if I was to do it again I'd do a smaller batch I had a hard time fitting all the grain and the pumpkin in to my Mash keggle. The porter came in at 1.094 and the ale was 1.044.
That thread had a lot of info. I'd say if you want you second runnings to be 1.060 your first runnings are gonna be in the really up there. RIS is what I'd shoot for.
Oh the one thing I didn't think about was a second boil kettle. once you have your first runnings, you'll need something to catch the seconds in.