If it has wedgits, .686 is fine. Wedgits rule. Or a non PPS version of wedgits.
Doubles aren't the most efficient, for whatever reason..40 shots total with 2 12ies as posted above is pretty realistic, but thats just my guess.
"I'll see it when I believe it"
PSA: Please don't use photobucket to post images. When you go through one of the older picture threads and find a lot of dead photo links, it is because of photobucket. They limit the amount of bandwidth your free subscription pictures can use, and then make the photo unviewable. Please use imgur.com or another free image host that does not ruin picture threads.