Improved cockpit drainage

I have a NorthShore 38 which has a very long cockpit and drains in the floor of the cockpit which undergo a 90 degree change in direction towards the stern and exit through the rearmost vertical extremity of the swim platform just above water. As the swim platform is an ad on the length of the drainage pipes has been extended and it seems to me that the diameter of the exit holes just above the water line has been reduced in the process. In any event even if it wasn't reduced I think the drains are inadequate and I don't even like the offshore racing rules which say that the cockpit must drain within 90 seconds. If the conditions are bad enough to flood your cockpit you may well take another wave on board well Inside 90 seconds and I shudder to think how my boat would handle with the cockpit entirely full of water in the meantime. My idea is to take two 100mm sewage pipes from the rear wall defining the cockpit just above floor level through the lazarette and then out to the position indicated in black in the attached picture. There will be multiple joiners in the lazarette to facilitate access to quadrant etcetera. Can anyone see any downside to this arrangement and anyone think I need some sort of flapper valve on the rear outlets? They will be angled slightly downwardly towards the transom outlets.