Weight seems to be a tricky thing with planes. What seems overly heavy for one is fine for another.

Tower lists the Big Stik 40 at 6.5 to 7 pounds, which I assume is flying weight. Greatplanes.com lists it at 5.3 pounds. I wonder if GP is only weighing what's in the box or if the Tower site has a typo.

Horizon lists flying weight for the US40 as 5 to 6 pounds.

Randomly looking at the advertised weights for 40 size aerobatic planes they seem to range from under 4 pounds up to 7. A lot list a 5.5 to 6.5 pound range.

My brother's US40 with OS-70 Surpass weighs just under 6 pounds. My Astro Hog with OS-70 Surpass weighs 7.75 pounds. They aretotally different planes but the engine seems to be a perfect match for both.