[willy]

rrichar I do not know all your answers but the weight on the back does make a difference in where those thru hulls sit in relation to the water line.
The cockpit drains called scuppers have enough pressure from the water weight to push it through.
But if they are sitting at or in the water line, or get that way thru boat action on the water, water will go in and out. It is a pain in the arse sometimes.
The main way they work best is under power moving forward. Even slowly, the pressure from the water forces out the thru hulls pretty fast.
As far as wiring I would wait for one of the masters here to fill you in, or just follow the manufacturers instructions.
**** A word of caution, plugging those thru hulls from the outside is dangerous. If you catch a good wave your boat will swamp immediately and you will have tough time getting to those plugs fast enough.
Remember that if you do take on water, keep the boat moving forward under power and the cockpit will drain.********