I don't really know. I am just starting to formulate my own recipes using Beersmith as my crutch, but I happened to remember that wheat trivia from back in the day.
I have been trying to clone a Deschutes Brewery Black Butte Porter, and most of the recipes I've seen (based on Jamil's recipe I think) include about 8-11% wheat malt. If I were going to brew this recipe, I think thats about where I would start. You have about 16 lbs of grain in your recipe, so I think I'd target about 1-1.5 lbs of wheat malt. I'd probably get there by reducing the 2row by 1-1.5 and replacing it with wheat.
Is this the correct answer? I don't know, but that recipe looks similar to the Porter I'm making, just stronger and without the dark malts. One nice thing, the wheat will give you a nice head.
Maybe I'll give it a try after my black butte!
nate
P.S. I don't know why the brewery wasn't more forthcoming, maybe they were being perfectly honest and the Jolly Roger is one of the few beers they brew without wheat malt?