thanks aquanerd. hey DB, i slept on it and finally figured out what you ment by "hole" ahhhh(shoot me lol).
ok so im sorta changing the design. aquanerd, i havnt done this tank yet...i want to learn EVERYTHING to a T before even daring to drill my first hole lol. anyway, this design is gonna be in asia, "they say" that water is fresh, clean and free of chlorine, with that said im basing this set to that. i would still be cautious and might to what you recommended (carbon filters, etc) just to be on the safe side. when i get there, im checking out water parameters just to be sure, incase of chlorine or god forbid, chloramine i would prob have to modify this set up a bit.
my main concern is really gravity. i have never had a sump or drilled tanks before. been always comfortable with the security of my ever reliable canisters

lol so all this overflow, drilling, etc is somewhat new to me.
thanks so much