Guys i'm getting ready to drill my 75 gal tank to cycle through my 29 gal fuge, its going to be gravity fed to the fuge and pumps back to up to the dt.

1 what are some ideas for optimal placement of the holes?
2hole sizes?
3ideas on over flows/covers to help and hid the holes in the dt?

I like to use a horizontal overflow, mine has 4 1" drains across the back and top of my tank. you can see it in my build thread, http://www.talkingreef.com/forums/member-tank-projects/6148-nay-kid-s-150-progress.html
As for hole size a 1" bulkhead drains about 600 GPH if its at the bottom of the tank and about 400GPH if its at the top. You can figure out how much flow you need depending on return pump and head loss. My overflow box is made of glass but could easily be done with acrylic, black to hide the bulkheads. Just my two cents

I would use at least two holes in case one gets clogged. If you can you could use a 55g or a 60g as your sump to add more volume and still fit in your stand. As for the overflow boxes you can call a glass shop and have them cut out pieces for you or find someone that does acrylic. With glass you can just use aquarium silicone to glue it together, downside is theres no teeth in it. acrylic I have no idea how to work with. As for your return lines theres many options, you can come over the top with pipe or you can add another bulkhead. Hope this helps.