Sheesh. So many talkers not enough listeners.
Stealth is not just about radar stealth mate. The more you HIDE your exhaust and nozzles (hottest parts incase people cant figure that out too) better your INFRARED spectrum stealth. It is embarrasing as a Turk to have to spell it out this to so many people on a Turkish forum like this. Not a single person could figure out what I was talking about?
I clearly said heat signature yet they are still talking about radar stealth. And yes knowledgable westerners from other sites are NOW also saying same things including head of the plane being too large thus nonaerodynamic and slower than F22 despite having almost the same thrust. That is not a small MISTAKE either. Can anyone guess for which reasons?
Like I get where you are coming from (though you did mention RCS earlier):
Some IR signature angles would indeed be suppressed to some extent (w.r.t nozzle surface and maybe some portion of the plume) by having the vertical stabiliser fully adjacent (red) and a bit more aft, rather than situated on the nozzle curvature where it is.
I really don't know where this stacks up in the trade-off analysis overall though given large circular nozzles have been elected for to begin with (i.e a conventional approach to focus on the front hemisphere RCS far more and optimize/economize overall investment in design and production).
i.e would say a small X% improvement here be worth it for other reasons the vertical stabiliser is where it is (I would venture mostly to create the space in the middle for a potential future sensor or other payload placement....while not altering the yaw-roll coefficient set by other geometries/weights too much and having to de-optimise those in a feedback loop and maybe other such issues too)
The F-22 is really the only stealth fighter that invests heavily in the rear signature suppression (of both IR and RCS) profile to the degree it does....and it was clearly a ground up decision from the get go (cost was really no bar there).
Make from that what you will.
Maybe other members know more about IR signatures (or other reasons) or can look it up to post here.
As for the front profile of the aircraft looking a bit big, people have already mentioned the CFD analysis that would have been done for that....as to trade off there w.r.t say the jet intake shoulder is done and so on (slightly different to say F-22 which goes for more width there). I really couldn't comment on it without looking at those details.
Anyway I'll join the conversation again a bit later.