For a front carry, a FWCC will use more wrap. Here is what I find helps me most with that carry. I would start with this one, and then once you have that down, move onto another carry (BWCC or Double Hammock). Without holding baby, I wrap place the wrap across my chest with the middle marker centered, then cross each pass behind me and bring over my shoulders. So I have 1/2 of a FWCC already done on me. Pull tight. Loosen just enough to get baby in, making sure to keep your shoulder passes nice and tight. Once baby is well positioned, take both passes in your hands. Cross over baby's legs, and meet your hands together with the passes under baby's butt. Swap passes so each hand now has the opposite side. Bring the passes under baby's legs and around to your back, making sure to keep pulling tight while you bring the wrap to your back. If you still have a ridonkulous amount of wrap left, swap hands with the passes at your back, and bring the passes back to your front, going over baby's legs. Tie a knot under bum.
I have a size 6 wrap that is on the long end of size 6, and I can FWCC wrapped around once and tied back under bum. And I have been known to ruck with a size 6, by doing a normal ruck, but instead of tying in front, I just continue to wrap all the way around and tie under bum.
And unless you are a really plus sized mama, a size 6 should be more than long enough. If you love love love the wrap, but just need it shorter, determine what size would work better for you, and have it hemmed down to a more manageable length.
Hope all that helps!
Cristina, Mama to Michael 03-16-06 , Nathan 01-16-11, and an angel 01-20-09
Go with your gut, follow your heart.