drain box capacity

My 313gal FBX with a 9" square drain box is arriving shortly. The drain box has only 2, 1" drains to feed my 2" line to my fish room. Why is this you ask? Call it poor planning on my part, and I probably shouldn't have trusted the manufacturers rec. Anyway, salvage mode time and I get to go drilling into my beautiful new tank. My question: My drain box is centered in my tank as the tank is viewed all sides in our great room. There is no additional room in the drain box for additional drain capacity due to the dry raceway installed for lighting wiring. Is there any reason why I couldn't drill and install a 90 deg pvc elbow, say 1 1/2" or so, near the bottom of the drain box? This elbow or pvc line would exit through a bulkhead fitting in the side of the drain box say 6" or so from the floor of the tank and come out a few inches into the display, make a 90 deg turn, and then exit through a bulk head fitting in the floor of the tank. Is there any reason why this wouldn't be a simple solution to my problem of low capacity to my fishroom/sump/refug? Also, in case anyone is wondering, I'm planning a 2" closed loop system for primary water flow through the display....My concern above is getting enough water to my fishroom for filtration.