The E-7 uses an integrated top hat configuration and not a balance beam. The antenna design was dictated in some part by the platform. They wanted to create a new class of of AEW that sits in between the widebodies and and small business jets yet had the persistance and crew to perform long duration missions (which they've demonstrated amply in operational scenarios) which was what the business jets lacked. A larger, higher drag and weight antenna would warrant a larger platform. Which was my whole point in the previous post IN THAT it is going to be extremely challenging to mount the larger chappati on a narrowbody without some severe degradation in aircraft performance. This is has never been attempted before so is an additional layer of complexity if one goes with a radar and architecture originally designed with the A-330 in mind and then tries to make it work on an A-320 or 737. That'll be a very high risk proposal.
For the UK and Australia, they simply aren't involved in large scale battle management with lots of different aircraft.
Britain is moving from the E-3 which is what the role it had performed within NATO and broader coalitions i.e. battle management at distance range and coordinating a large coalition of diverse aircraft. Australia likewise has been doing those sort of missions in its initial deployments with its aircraft. The narrobody will get you into that sweetspot and that 80% solution but that requires some design changes and trades to optimize for that platfrom. Had Northrop Grumman or Boeing tried to mount the E-3 or E-767 radar and mission system on the 737 they would have failed miserably. Platfrom limitations and other requirements ultimately dictate sensor and command and control mission system margin. If you go down a path of a 737 or A320 you have to design everything to fit that.
Short of a wholesale transplant of an existing smaller jet radar (like the E-2's, Netra's, or Globaleye's) the tophat configuration is probably the best approach/outcome one can hope for within the size, weight and drag margins of a 737 or A320 unless one compromises on other performance requirements. If a last minute decision is made to go for A320 or 737, I suspect that the radar and other design elements will need to be re-worked in light of these smaller margins, tolerances and other performance degradations on account of drag, weight etc. It is probably not worth the extra effort and self-imposed risk. Better to go for 767 or A-330 as was originally planned. Alternatively, if financial limitations continue to persist, mount the Netra radar and suite on a new platform that has more endurance. That will get tails in the hands of the IAF faster. But trying to squeeze a radar and mission suite originally envisioned for a widebody into a narrowbody entails considerable risk and could potentially bog the project down once they get into the thick of platform integration.
