Shrink recipe 6.5 gal. to 5 gal?

[harderj1]

I'm about to brew a Papazian recipe, Limnian Wheat Doppelbock has anyone tried it? Anyway, his recipe is for 6.5 gallons using a 4 gallon boil. I'd like to reduce the recipe to 5 gallons. How do I reduce the recipe without altering the end result? I'd like to boil at 3 gallons. If you haven't figured it out already I'm a math idiot! Thanks for the help. Cheers!