My cockpit drains are halfway between the transom and the bridgedeck, crossed below deck and are slower than I think they should be. I plan on a large drain through the transom on one side as I have an outboard rudder. The original drains will get any water left if heeled. My cockpit sole is 8" above the waterline at rest.
One reason I think for the forward drains is that for crossed hoses to work best you need them to be on a steep angle and not a shallow one. Most hulls will have more depth forward.
Living aboard in Victoria Harbour