Channeling is a concern when fly sparging only. With batch sparging you're stirring the sugar into the water, not relying on a balanced gravity feed to rinse. Feel free to run it as fast as you can. In fact, the faster the better. It lets you get into the kettle and on your way to a boil before enzymes or pH can present problems.
So I'm not meaning for this to be a Palmer quote fest but it's going to have to turn out that way. Everything I've read (even Palmer) says that you need to run the drain slowly. Even if you're stirring vigorously as you drain you'll leave some sugar behind. That's just my understanding and here's my first quote from Palmer:
"Our goal in the lautering process is to rinse all the grain particles in the tun of all the sugar, despite all of the non-ideal conditions. To do this we need to focus on two things: keeping the grainbed completely saturated with water, and making sure that the fluid flow through the grainbed to the drain is slow and uniform."
If that only applies to fly sparging then that's my bad and something that's good knowledge. Because, like you said then I can just let 'er rip.
The other thing you'd asked about was why keeping a manifold pipe away from the wall is needed. When you have one of the manifold pipes up next to the wall the water is going to take the path of least resistance. That's going to be down the cooler wall 10 times out of 10. So you'll be leaving some of your sugar behind.
From Palmer: "In addition, it is very important to avoid channeling of the water down the sides from placing the manifold too close to the walls. The distance of the outer manifold tubes to the cooler wall should be half of the manifold tube spacing or slightly greater. This results in water along the wall not seeing a shorter path to the drain than wort that is dead center between the tubes."
As for the single braid vs manifold, Palmer has illustrations showing the difference on his site.
http://www.howtobrew.com/appendices/appendixD-2.html
Like I said, I follow Palmer's guides on pretty much anything and will be getting his books Water, Hops, Yeast and his soon to come out Malt book.
But in the end if you're getting 75-80% don't mess with success!!