Add soft tape measures, the kind seamstresses use, to all the grab bags for the "Open" at Clear Lake and take the time, during the tournament, to talk about getting the estimated weight by:
(Length X Length) X Girth then divide the answer by 1200

Encourage people to take cameras. Even if they are only disposables. And take lots of pictures from multiple angles to get all the colors of the fish.

With all the measurements, tons of photos, an accurate fiberglass replica and a really good airbrush artist, you can a realistic mount.