Use the search feature and I'm sure you can find LOTS of posts regarding cooling lines.
1 st question, is it a basically stock ski? Do you have plans on running single cooling? How cold is the water you normally ride in?
I say for starters, why reinvent the wheel and just use Factory Pipe instructions.
You could improve it by using a Y or T fitting and splitting the single into two for a more even cooling for each cylinder by drilling the exhaust manifold for a 2nd fitting, same with the out going lines, if your using a stock head you need to drill the front on the stock head for a 2nd fitting, then Y or T back together to feed the headpipe. Then out of headpipe to a t and a bypass then on to the stinger at the end of the chamber. If you want to get more creative, get a Jetworks Flow Control valve and put it inline to the stinger feed. If you do this you will need to fuss with the low jets to work really well.