The earliest 35X, also known as the Blue Ribbon Special, was slightly lighter than the later X motors, and a first version VooDoo balanced close to OK with those. I never weighed either a Series 1 or 2 Combat Special, nor the Series 3 (two piece case, and heavier), but a Rocket 35 is/was the same 7 ounces as a Johnson, so the silver head and black head CS were most likely about the same.
Back in the day when a VooDoo, or Sneeker, Big Iron, or Ranchy were all competitive, I had more Raunchies and Sneekers than any other, and mostly Fox 36Xes up front because the Tigre G21/35s I had then were too prone to eating cranks, and I either had trouble getting Johnsons, or chose to avoid them because of the weaknesses in the design (cannot recall any more). I was using longer booms already, before I heard about or saw a Nemesis, although my Sneekers flew quite well with short booms.
I saw Riley's Sneekers at contests before he switched to Demons, and got a set of rib patterns from him; the span was 42", not 36", like the kit he produced a little later. Mostly I built that larger one, even though with the extra wing area it was slightly slower than a VooDoo -- the big Sneeker turned very tightly with far less drop in speed than a smaller plane.