Cockpit Drain Above or Below Waterline?

[Paul Mazza]

Hopefully this is the right forum for this question. I've got an Endeavour 37, which we plan to do an extended cruise on. I'm struggling with the large number of large below water thru-hulls. There are seven 3/4 to 1.5 inch thru hulls plus 2 small chain locker drains all below the water line. Here's my question:
The cockpit drains are 1.5 inche dia. and drain to thru-hulls approximately 2 feet below the water line. The cockpit floor is approximately 21 inches above the waterline. Can I move the drains to an above the water line discharge maybe 15 inches below the drain, and 6 inches above the waterline. Perhaps by putting a check valve on them to keep a wave from pushing water up into the cockpit.
The other question is: Do sink drains need to be 1.25 inch diameter. It's seems odd to have a tiny head sink, draining into a giant 1.25 inch thru-hull. Do people have smaller drain lines? Any advice here would be greatly appreciated. Paul