http://forum.topeleven.com/formation...ation-use.html suggests 4-1-2-1-2 Narrow Diamond.

That said, you are right that the midfield is what is important. I see no problem using 3-5V-2. Attacking, Mixed, Whole Pitch, Normal, Long, Zonal, Off, On. As for arrows, I'm not too sure... last I played 3-5V-2 I used red forward arrow on DMC and blue defense arrows on both MCs.