I brewed a pliny the elder clone, but not the one you're specifically referring to. I used a recipe that was allegedly published by the brewers (it's listed in a thread here, but PM me if you want it and I'll dig it up). It was absolutely outstanding. I've not had the original but a friend who did said mine was very very close - only lacking slightly in 'maltiness'. I did miss the target gravity though.
To answer your other question - yes, you will lose a heck of a lot from the hops. My pre-boil wort was something around 8--8.5 gallons, but by the time I racked I was left with thirty 500 ml bottles. I also recommend the use of pellet hops over leaf. I had a mix of the two and the leaf hops made racking extremely difficult (unless you have something to strain with in the process).