If anything, I actually agree with Dino - an attempt on another motherboard shall be made.
This is not the first case when I see Crosshair V Formula boards produce results that are not in line with reality (reality = results done on other boards). As some people probably know, me and websmile (a guy from Germany) are between the most active DDR3 binners in Europe. We have a very clear idea where the tRCD walls and MHz/volt scaling limits are for most ICs. None of us has a C5F, but the C5F results we see from fellow binners (sometimes with our ex-kits) usually greatly exceed what we thought was the max of specific kit or IC. So, for this matter, I, personally, would not recommend relying on memory overclock results made on C5F when looking for pre-binned memory (unless you're going to run a C5F as well).
I could be wrong and the board is an engineering masterpiece so, don't take me 100% seriously.