need suggestions on my return! plz help!!!

[golfbomber]

i am setting up a nano tank. dimensions are 24Lx18Wx16h so that makes it 30gallon. i am partioning the back for another 6 inches for my skimmer and fuge and return. as this being my first nano i am thinking of running a mag 7 for my retun (i have a new one sitting around). so how big of a hole should i go on my return? i was thinking drilling a 3/4inch then using a loc line t adapter for 2 arms of 1/2 inch loc line. is this way to much flow???