Having lived on Maui I can tell you that bones very well may go up to 20 pounds. Though I have caught them on the few flats that exist on Maui with a fly rod. The real action is fishing conventional gear off of Jetties and old piers. Best bait was a cut strip of Ika,(squid) fished just off the bottom. We would use 20 lb test but 6 pound test to attach an old spark plug as weight. When the fish took the bait the spark plug broke off and the war was on. Even on a medium salt water spinning reel or a Pen Jig Master reel like the ones used for stripers your chances of landing one of the big guys were slim. Some of the big guys could run most of your line out on one continuous run. I mean they wouldn't even stop for a few seconds rest or turn in a different direction. Most of the time your line got cut on the reef or as the fish entered much deeper water a shark took advantage of the situation. Did see a local land one one evening just before dark that was about 13 to 15 pounds, very big with wide shoulders. The guy was using a pen reel, I think it is a 6.0 reel it's the one they use over there for Trevalli. The bone fought like a 40 pound trevalli.
Locals do eat bonefish and the meat is highly prized for Sushi or for fish cakes.
I've mentioned this before as how the fish is prepared for consumption. You put the fish in a brown paper bag and put it in the fridge over night. Next day you cut the tail off and you do not gut the fish. Put the fish on a cutting board take a rolling pin, most people over there just use a large glass coke bottle. Roll the both sides of the fish towards the tail and the soft meat comes out just like tooth paste coming out of the tube. The meat has a strange color sort of light pink with some silverish color to it, just how you look at it in the light. I have made the local traditional fish cake out of it and it was very good but different than any fish I have ever tasted, sort of a metalic taste when it first hits the taste buds. For a local from Hawaii who fishes the great dream is to go to Midway or Christmas Island to catch bones and trevalli. I have been at the Maui airport when flights have come back from such destinations and the locals guard their coolers full of Bonefish.
It was really interesting to read the site mentioned above. Never knew that bones were found in waters such as S.F. Bay, seems just to cold. The bone is truely a world wide fish as I have caught them throughout the Pacific Islands and the indian ocean. Lately I have sadly thought of catching them in the Andaman Islands way back in 1972 or 73. Now I can only think of all the wonderful people who lived in fishing villages who lost their lives to mother nature.
I bet that more than half the worlds bonefish flats have not been fished yet by a fly rod.