Thank you gentlemen, I enjoy building for others as much as myself. I get to build beautiful aircraft and it don't cost me a dime, doesn't get any better.
Wade, the difference between Ultracote and Stits are night and day. I can't give you any hard numbers right now but I would guess four to one in weight difference if not slightly more. And for a bird of this size that is a big difference, once I get a roll of the Ultrcote I can tell you better.
Stits starts with polyester which weighs near nothing but light ends there, next up is 2-4 layers of polybrush, 1-2 layers of polyspray, 1-4 layers of color, plus the stitching and tapes. The Eagle came out to 48.5 lbs, it was 50 on the nose until I rearranged the components and removed the weights.Wow!! I'm really surprised by the difference. And yes, with something as large as your Challenger, that's huge.
What is the weight of your S1? I realize you added a ton of scale detail, that won't be on this one.