After more testing, Not as stable at 3200 as I first thought. Won't boot from cold. Have to boot at 2666 into windows first then switch over every day. But proof it works. Just the trimming on post when cold that has issues. Have yet to try LN2 mode.
Also does not like to run with overclock either. Can manage 4.1GHz at 1.425v stable. Not running 24/7 just testing. The new bios should be out soon that will fix the cold boot issue with 3200MHz and hopefully allow for overclock with that as well.
But yea, G.Skill with the C6H is the only board I myself have managed 4x16 and I have seen others manage 3200 with 2x16 and 4x16. Not many but not a common config.
But when buying G.Skill and going 3200, Don't go 3200 C16. It isn't b-die and so you will at best see 2666 if posting at all.
You need b-die if you want any chance of running dual rank memory.
Also anyone buying the C6H, First boot, set the SOC voltage to 0.95v and flash the 1001 or 0032 bios from overclockers.net discussion. It will remove any chance of killing your board through a bug from launch day.