Drilling a 210 gallon Acrylic tank

I just bought a 210 gallon tank to whom I want to do coral and fish, and I plan to do the drilling for the bulkheads myself, so my questions are the size of holes I need to drill ? I want to do 2 overflows boxes made from 2 4" round PVC pipes, and I also want to place the return & drain in the corners of the tank, so what size overflows do I need to make ? and bulkhead holes I need to drill, and what size holes do I need to drill for the return and drain bulkheads ?