Actually studying some online juvenile bass pictures the SMB clearly have an 'underbite' with lower jaw protuding more than these pictures above have. It is the large upper lip and the upturned mouth that is prominet. The juvenile SMB and even LMB have 'thinner lips' or thinner lip profiles.
I was looking through the pictures on this page and found it helpful to see similar sized fish lined up to study their mouth/lip structure. In fact the 'Warmouth' on this link has some of the body morphology features and lip features that the GSF have but minus the vivid yellow coloring of the pictures above. Also doesn't have as large of an 'eartab'
Is there agreement on what a warmouth is or is it different species in different states?
Very awesome fish!!
Fish ID page 
