I do not know how big too big is for LMB, but a few weeks ago I mouth hooked a 6" sanddab on a 5" swimbait. Also, using a swimbait in New Jersey, I once mouth hooked a 5lb bluefish that came in with a 3' eel sideways in its mouth.

On the other hand, my son recently was fighting a two pound trout near the bank when about a four pound female and a somewhat smaller male pair of LMB came up to investigate the trout. The two bass oriented within a few feet of the tiring slowed down trout for quite a while but never went after it (my son stopped reeling the trout when the bass appeared to see what would happen).

Bob