everything above the waterline can be drilled and screwed - as for the cleats they are mounted via screws or bolts.
battery case makes it easy to load /unload battery while launch / wrap up - also it keeps it protected from water and shorting out
Nice pick up. Some of the other guys with boats like that have added some nice mods. Check out this thread
http://www.mafishfinder.com/phpBB2/team-beaver-fever-budget-bass-jon-boat-build-t5433.html