OK, I've done a few back of napkin computations using Clare's measurements and I have good/bad news.
Fortunately, the front support is fairly close, maybe 1/2" scale too thin.
The stabilizer isn't as bad as I thought, maybe 3/4" scale too thick although I think the cross-section shape is dubious.
So why does it look wrong to me? There's not enough room to build in a proper rudder actuator rod.
So, apparently the tail end of the Pegasus kit tapers too quickly which made the stab/rudder look too thick. I've guestimated the open tail end area of the fuselage to have a diameter of around 8.7". The kit scales to about 2" here.
I'm going to take a picture of the kit tail and try to overlay it against some pictures to see if I want to take this any further. :(
--David