Q1. I have not seen the tutorial but I am guessing the intent it to separate the entire cone shape and then split that edge so it can be unwrapped.
Think of it as a piece of paper wrapped around an ice cream cone. If the paper was glued along the seam, you could not make the cone flat. But if you cut along the seam you could unroll the paper into a flat piece.
Q2. Not 100% sure why shells shrink when they are unfolded (I believe maya is trying to normalize the shell relative to other shells in the texture region), but I usually can prevent it by pinning some of the verts so they cannot be moved. For instance pin the top half of the shells uv's, unfold, then pin the bottom half and unfold.
"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675
Last edited by ctbram; 06-03-2012 at 06:46 PM.