i did a class once at an expo on Y seams. Everyone else had taught to mark the 1/4 inch spot on both pieces and sew from the middle toward that spot. She taught to start at that spot and go toward the middle. It actually makes sense considering the bias you would be sewing on that quilt. So i'd starch the heck out of the pieces, and try that. She may have also alternated when there were multiple point: start from outside edge on one piece in the block, start from middle in the next piece, etc.