on a 150 your going to want more flow then a 3/4 return can give. I have 2 1-3/4 holes with bulk heads in the upper corners with a hang on return. I believe there 1 1/2 return bulkheads. You can drill another hole for the return also.
Is the bottom tempered glass? Make sure its not before you drill.
Make sure the sump is large enough to hold all the drain back. There are ways to make them quiet if you get the gurgle(sp)
I would research on the flow rate before you settle on one hole that small.