bulkhead sizes and drilling

I'm going to be drilling a 72 gallon bow front, on the back side, to install
a sump. I knew I didn't want my drain holes to be too small, so I ordered
1.5 inch bulkheads. The hole has to be 2 3/4 inch though, which I didn't
realize how big that was until the bit showed up. Should I be concerned with
structural integrity with a hole that size? I was planning on two drains on
each end and a return in the center, but do you think I should just have one
drain?

Rick