Here are the forward, rear and the afterburner exhaust duct assemblies
I had to cut the rear frame inside to accommodate the duct
and here is the fuselage assembled
aft end looking in without the exhaust duct
and since the duct is slipped into position from the rear, I added 4 L shaped card support that will bend forward when pushed by the duct. Those will act as springs, center the aft end and support the duct.
and the duct in place ( not yet glued, but you can if you want to at this point ).
Isaac