missed OG by 15 points!

Hey guys, I need some help. This is my second AG batch. I hit the OG spot on for my first batch (1.050) but winded up being 15 points low on this one.

Here is the recipe I used. It is for Pliny the Elder by Vinnie. I ordered the Pliny hop pack from one of the vendors here.

11.5 # Pale malt (2-row)
.5 # Carapils
.5 # Caramel 40L
.6 # Cane sugar

3.5 oz CTZ 90 min
.75 oz CTZ 45 min
1.0 oz Simcoe 30 min
1.0 oz Centennial 0 min
2.5 oz Simcoe 0 min

Mashed at 152 for 60 min, sparged with 3 gal @ 180F and 2.2 gal @ 170F

I boiled for a total of 105 minutes, and still ended up with over 5.5 gallons. I was shooting for 5, so that is partially the issue, but I ended up only getting an OG of 1.055. The target OG for a 5 gal batch is 1.070.

My question is what might have caused this very poor efficiency given that I had hit my target OG the prior night with the same eq/setup.

Also, what can I do at this point? I've got about a cup and a half of headspace in a 5gal Better Bottle, so a little more than 5.5 gallons. I've pitched some Safale-05 and cooled to about 60F. Can I just add more sugar to get the additional gravity points? Or would that dry out the beer too much? Maybe I could try some DMT?

DME to the rescue. You'll probably need a couple of pounds in 2-4 cups of water. (You can probably look up the real numbers online somewhere)

There are a lot of Pliny recipes out there, but this one looks short. The one that was published last summer in Zymurgy uses 13.25 lbs 2 row, .6 lb Crystal, .6 lb Cara-Pils, and .75 lb corn sugar. Those extra sugars would make a big difference in your OG. With this recipe, you have to calculate like it is a larger batch because you lose so much wort to the hop trub.

Beersmith gives an OG of 1.067 for a 5.5 gal batch. I'm going to end up waiting a week for primary fermentation to complete mostly, then rack to get more headspace and add around 2# of light DME. Shouldn't be any problems with that , right? I also have some slight doubts about the IBU just because I used cheesecloth to hold the hops and they became really packed and hard when they soaked the wort up so I'm not sure that all of the hops acids were 'isomerized'?