We basically arrived at the same conclusions here. I also struggled with that section when I was modeling mine. The distance from the canard trailing edge to the wing is definitely longer than from the leading edge of the canard to the nose. I went with a YF-23 sized plane (68 ft) + an F-22 sized cockpit (11 ft). That gave me a rough idea of realistically how long a chord length I was working with at the wing root, which in turn gave me a somewhat more believable distance between canard and wing.
I must say as far as aerodynamics go, I'm not super knowledgeable so I'm basically just guessing for the wings and exhaust
I also tried the wing shape you had, but one thing I struggled with is thinking about wing span vs the length of the plane. For what we both arrived at, the width of the wings are approaching a 1:1 ratio with the length, which ... I'm not sure whether that's desirable. Looking at the J-36 though, the wingspan is definitely approaching a 1:1 ratio and only after trimming the wing tips did I arrive at a similar aspect ratio.
As for the exhaust, I assumed 13 ft long engines but lengthened the exhaust considering the giant paddle exhausts we saw from the PW video. Or else without that added length, I could get it down to F-22 size.
For the angle of the gull wings, I ended up going with a 10 degree dihedral followed by a 12 degree anhedral, which seemed to blend well angularly with the angles of the fuselage itself.
I'd really appreciate someone more familiar with the aerodynamics and tailess controls to bestow some further guidance on the wing's shape, taper, and the exhaust section.
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