RE: 42"wingspan p51d what size engine?
You're kidding right? I've been building models since 1968 and have never heard of anyone covering a model with brown paper and carpender's glue. I would strongly recommend against that covering, unless you just want to add a whole lot of weight. Remember, the lighter the plane, the better it will fly. You lightest covering would be one of the iron-on films like MonoKote. If you're not comfortable with iron-ons, I'd stick with the tried and true dope and tissue. I bet you could keep the weight under 3 pounds. My IL2 Stromovik has the same engine, 3 micro servos, a micro-mini servo for the throttle and a 250mAh battery pack; and weighs 2 lb., 13 oz.