First: I'm constitutionally incapable of following the plans when building a cowl. Even for a scale plane I'll find a "better" way (which sometimes may actually be better) to make a scale-ish cowl. So take that into account when you read this.
Second: The whole concept of fitting a cowl that TF executed on the ARF nobler is just not going to fit well, or at least not without a lot of work. Shell cowls like that work well on airplanes that came originally with cowls that fit loosely at the back to let out cooling air, like light planes in the 1940's.
The only way I could see a shell cowl like that really fitting is if you glued a plywood ring into the back, either about 1/4" forward of the back edge so you can use the TF mounts, or right at the back so it fits up against the fuselage. When you try that, you'll probably find that the cowl is a bit big, and needs some wedges cut out of it to narrow it down (if I were going to do this on a plane of my making, I'd probably leave the fuse roughly finished, then finish it to the cowl contour -- which won't change now, because of the ring). By the time you're done, you'll have spent as much time as Ty, Ken and Craig did on theirs, and it'll still have that ugly vertical parting line.