corn spacing for poly culture

Have you ever experimented with different spacing of the corn?  I've read that some people plant four corn plants in a "clump" and each clump is spaced 3 feet apart on both sides.   The space in between is either cover crop such as clover or something along the lines of squash or pumpkins.  I can see even radishes doing ok in there early on.  I'd love to hear your thoughts on this idea.

I'm growing popcorn and sweet corn this year in an area that was tilled by pigs last fall.  I was planning on trying the above method. (spacing the popcorn and sweet corn in time and space to avoid cross pollination).  I always give the smaller cobs to the chickens and don't save seed (yet).  

Does anyone have any thoughts on this?  AND  what might be other cover crops to plant in this poly-culture?

I think this idea (of sowing in clumps) has been promoted by Jean-Martin Fortier. We already had a discussion a few months ago about that.

In my limited experience growing small plots of corn, I regularly had most ears of corn contain 60% or less of actual kernels. It was rather disappointing to shuck an ear and see sparse kernels. I would later learn the reason for that was lack of plant density, and the alternative to ensure complete ears is hand pollinating the silks. It takes a lot of corn plants for complete and thorough wind pollination of the silks. I didn't intentionally plant anything amidst my corn when I grew it, but my melon vines found there way into the corn regardless and seemed to do ok.

Craig Dobbson wrote: some people plant four corn plants in a "clump" and each clump is spaced 3 feet apart on both sides.  

That works out to 2.25 square feet per corn plant. Which I think of as the bare minimum that a corn plant requires. I would consider that kind of spacing to be fully planted, with little moisture, sunlight, or minerals left over for a cover crop. You could space the cover crop and corn plantings in time.  The cover crops I grow with corn are my typical weeds: amaranth, lambsquarters, Solanum physalifolium, sunroot. I typically kill the first cover crop immediately before planting corn.

Traditional (Hopi) planting of corn clumps spaces the clumps at distances more like 7 to 10 feet apart.