I just finished removing the fuselage, disassembling it, cleaning off the excess glue and/or plastic nubs, and then reassembling it. Difficult and frustrating at times, but the gaps are gone and the fuselage is now locked in where it should be.
Even more respect for the people putting these things together for us, and thanks to everyone here who has shared their past projects, particularly sh9000: seeing your separated VF-1D fuselage inspired me to give this a shot.