1. What are you talking about? Ground-based Low-Band radar detects the general location of an enemy stealth fighter and relays the general coordinates to an interceptor.
The efficacy of
GROUND BASED meters lengths systems against low radar observable bodies, even when those bodies are shaped to be against centimetric and millimetric freqs, have not been proven. The truth is that those meters lengths freqs have been employed for long distance before the advent of 'stealth'. What this at least implied is that the original designers of 'stealth', meaning US, investigated this alleged efficacy and found the technical and operational claims to be dubious at best.
Here is the proper definition of 'efficacy'...
http://en.wikipedia.org/wiki/Efficacy
Efficacy is the capacity to produce an effect.
Regarding the claim of long wavelengths 'efficacy' on low radar observable bodies, this has not been proven beyond any reasonable doubts due to the fact that no one have an F-117 class body to test out their claims. This fall under
TECHNICAL EFFICACY. The most the Russians can do is extrapolate from 'regular' bodies and hope the sales brochures works.
Since meters lengths freqs system must be ground based due to antenna size, this limitation fall under
TACTICAL EFFICACY. Just like ordinary human vision, radar is equally limited to line-of-sight limitations and being on the ground is the worst place to be if the goal is to be long distance. That is why these system try atmospheric 'bounces' to extend their reach.
Combine both and the overall efficacy of meters lengths freqs against 'stealth' in a tactical setting is dubious at best.
2. I said airduct-fuselage gap. I made no mention of the diverter assembly. Try reading my posts properly.
An aircraft is a vehicle in motion with complete six degrees of freedom: three linear and three rotational.
But what make an aircraft fly is the aerodynamic efficiency of the wings, not the fuselage. In other words, literally a brick can fly if it has sufficient propulsive power, efficient wings, and sophisticated flight controls to actuate those wings to compensate for the brick's 'blocky' or 'chunky' fuselage.
The overall 'aerodynamic' efficiency of an aircraft is about the amount of power needed to maintain stable flight, in other words, reshaping the brick's fuselage decreases the power necessary to keep it flying. Reshaping it further enough and eventually you will reach the physical limits you can without crashing this body. Now you need to address the weight issue. Hollowing out the fuselage further reduces power required to maintain flight. Do this enough and eventually you will reach physical limits needed to maintain fuselage integrity.
But we are not talking about a brick with wings versus a paper airplane. We are talking about two finely shaped bodies. So if you make the claim that the J-20 is 'more aerodynamic' than the F-22, please provide hard data.