Got this from a member on the aircraft resource center. This is his fix to make better looking intake. This will work for both the 1/72 and 1/48 models. The author is Gene K
I roll/wrap the pattern over a round file handle to shape it, then hold the compressor face in place (or a suitable disk) while gluing. After the duct has dried, trim the indicated inside corners square.
Next, insert the duct from behind by carefully bending the duct top and bottom inward to allow it to slip it through the fuselage opening. Once it's in place, the top and bottom can be "opened" and pressed into place inside the intake for a perfect fit (providing the pattern has been precisely cut).