The nice thing about a Baby Streak is that at its size, even an over painted one, weight-wise, still falls right into the performance wheelhouse of the engines most of us use, Tee Dee .049/051 and Big mig .061. I save a little weight by using a bladder, though not for that reason. After several punishing years of repairs, my red, white and blue Streak(I call it BFS-I) weighs a little over 9 ounces and a Tee Dee .051 with a 5.25"x3" MA prop still turns fast enough to eat its tail and handles the wind better than the 7oz one(BFS-II/Norvel). The main thing to avoid is making it too tail heavy, just as a good building practice. But after repairs, BFS-I has a slug up front and still flies like a dream. So don't fret over it too much. Just make it pretty and fly it. You'll love it.
I look forward to seeing your finished product, Dan.
Rusty