We ran our cockpit drains out the back like is shown in Gary's photo when we did the Dave King mod except we went through the back bulk head. We did that because we have all the house batteries in the engine compartment.
Water does sometimes surge up into the cockpit when severely heeled over. We believe most of this due to not having the ells up high enough, something we will eventually correct. If that doesn't work we'll put in check valves. If we're heeled over so water is surging we are heeled to much and not sailing the boat properly.
We considered crossing them over but were concerned that when the cockpit filled when heeled it wouldn't drain. I considered crossing them and tying them into one pipe exiting each side but it seemed like a lot of trouble and might slow down draining.
Jim