If his hips are truly not sound, then you will not be doing your breed a favor by reproducing your boy.
My suggestions yesterday was to RE-xray him and see if it was possible that the first set was poorly done. Maybe seek out a specialist in x-rays. When the dog is re-xrayed, ask the specialist their opinion without resubmitting, unless the second vet says that in their opinion, the hips are sound.
How do you feel his hips are? Does he bunny hop, even slightly, when running? Does he favor one side? Does he move at all stiffly? If he seems to be, in your opinion, solid in the rear, then it might be to yours and his best interests to get that second opinion.
But if you have noticed that there really is some stiffness...finish his championship and neuter.
As for using a Fair dog...IMO, if the Fair dog has a solid background of sound hips and is bred to an Excellent, then it might be OK. If the Fair dog has iffy dogs in their past, then it shouldn't be bred.
I don't think there is a lot of playing around to get favorable results, at least I haven't heard of this in my breed (Malamutes). OFA is pretty unimpeachable, with their techs simply reading the results presented and giving ratings based on the picture they see in front of them. Unless someone flat out cheats and takes in a different dog than the one they are truly sending in the results on, the dog will be given an honest rating.
Good luck, and I really hope that in your case, the first vet simply messed up a bit and a second reading shows that your boy TRULY has sound hips. But, again, if not, stick with your original plan and neuter.