I would check with one of our members that has a program that lists awards given to this cross. This way you can find out flower size and count on those awards and compare you plant to that info. If your plant's stats are better than the former award, then by all means bring it in for judging.
Generally - I would say that any time you need to ask if something is good enough to go to judging - it is good enough to go to judging. Judging is subjective, I have regularly seen plants I would not have awarded, get awarded, and the reverse, plants get passed that I thought were sure winners. If a plant is presented at that perfect moment, and you get a judge who is at his or her 'perfect moment', your plant will strike the judge's fancy, then 'voila' you will have an AOS award. You never know. Every flower, as it opens goes through that perfect moment where it really looks at its best, caught at that time orchids that don't quite measure up to the stats can still get an award. So if it is easy to get to judging I would bring anything you feel is decent or better. You never know, after a few months of this you might get something awarded. When I was on the campaign to get a couple AOS awards, I would always bring 3 or 4 plants, besides the one I really thought would get an award. With only a couple exceptions, it was always one of the 'other' orchids that got the awards. Support your local judging center, show up with a few plants, they will appreciate the effort. Of course I am lucky enough to live within 50 miles of a judging center. If you have to drive hundreds of miles to get something judged, whether or not to go is a real commitment.