See if this helps: You Tube video by Kaye Woods
http://www.youtube.com/watch?v=XLkHfcuNzCA
if the link doesn't work go to You Tube and search for:
Y-seams. They're easy with Kaye Wood's techniques!
There are other postigs on You Tube for Y-Seams - helps because you can see what they are doing if its a good video.