now this is an interesting topic please keep us posted. There is a video somewhere on the net of a guy building a large peristaltic pump for a gravy shooting fountain as a special centerpiece for thanksgiving. Might give you some more ideas. It is at least quite funny/disturbing to watch.
I got this idea from this forum and it works great. A piece of wood with a large hole in the middle. Large bolt with big thread goes through hole and connects to vinyl hose to HLT. sparge water flows through threads hits the floating wood and is dispersed over grainbed.