I seem to remember when TA&M was working hand in hand with the TP&W researching LMB back in the 80's and 90's. Lake Fork and the fish in the lake were studied. I read where they would catch a large lmb(can't remember the sizes but they were larger sized) and add a transmitter in the fish prior to release where they could study the patterns and or whatever. Re-catch the fish a year later and I believe the fish had added some weight. I don't think it was a lot of weight but there was an increase. Hay! I would not bet my life on it , but I think I remember stuff like that back then.
The share a lunker program is about using the fish for reproduction of the genetics, so I would expect the lunker's to lose weight in captivity. Bob Lusk says moving large lmb to a new place they will not adapt and lose weight.