I wouldn't add a real cleat. A real cleat would end up getting used as a 'cleat' somewhere along the lines and, as mentioned, it may not be in an appropriate spot (you may have access to thru-bolt, but might have to remove something or get up underneath). Why not just use the existing midship cleat?
However, a fender cleat (look on Taylor's website) would be appropriate. You could also mount it to the gunwale (which is likely even more robust).
A pic of the area would help, though.