Rice hulls will definitely help. It's not so much the manifold design (although that is a factor) as the fact that wheat malt can setup like glue in the grainbed itself and prevent good sparging/runoff. The rice hulls just break it up a bit and let the wort flow.
I've noticed with high %'s of wheat and/or rye I sometimes have to cut the top 1/2 of my grainbed even with rice hulls in order to prevent a "bathtub effect". I generally try to avoid it however, since it can lead to channeling.
Baron, since you're a decoction master, do you still add the rice hulls at the beginning when you're doing a decoction? I wasn't sure if they wanted to be boiled, so I just added them after I did the decoction (screwed up my temps, though).
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