wheelies in general slow you down, its added wind drag, engine stress, and less off the line grip.
the best thing you can do with any wheely monster that you just want to remove the wheely bar and place the batteries in the middle of the chassis, and soften the rear shocks. it will squat and shoot off like a rocket, and will prevent you from flipping over. my mt with a cv-r .18 is stupid fast off the line and it tops out at about 43-45mph around 2.7 secs, and i can peg it and dont have to worry about flipping over (except when its lean and on cement)

and all wheel drive adds bearly any weight, its like adding another 2AA batteries and thats it. most your weight comes from the suspension and tires.