there's no such thing as over leveling unless the game allows you to break the level cap established by that game usualy 99... Lvl 40 at the Temple of Ancients? that's still low in my opinion, heck, i always gain about 10 levels before moving on anywhere, usualy about lvl20 or more before i ever leave Midgar, and 30+ by Junon... Killing the Midgar Zolom a few times before crossing the mountains really helps those levels go up fast, don't need no Chocobo to cross the swamp, if ya do then you cheat yourself out of the Enemy Skill Beta early on which is quite possibly the best Enemy Skill that early on... now this of course does not apply to games like FFVIII where the enemies level up with you in which case you want to take the opposite approach and try not to lvl up as much as possible... really when i see threads saying things like the Demon Gate or RAAPS were hard i always question why they think this till they mention their levels which are usualy abysmal... honestly i've never tried playing anything under-leveled, i usualy grind an area untill it no longer benefits me...