Hi Ian,
Are you a company or a manufacturing modeller? I would be interested in seeing some of your products, do you have a web site?
only thing I can say is that the GR3 is infact an upgrade of Airfix's original GR1, this means that the GR3 has a solid nose until it gets to the original GR1 nose shape, if you know what I mean, so this may present a problem when trying to mount the replacement nose?
Anyway thanks for responding to my question and I look forward to hearing from you in the near future.
Doug.