Take a look at some of the youtube videos of long armers quilting out extra material on quilts. It will give you an idea on how they do it and how it looks. I think 505 is the way to go for basting as it holds better than pins. It also lets you peel up the fabric and reposition if necessary. Using a batt with extra loft can help with extra fabric in a top also. Continuous quilting designs can advance a problem area ahead of the needle so use some isolated designs to confine the problems, not just move it along. A lot of long arm quilters use a bead board motif on borders for wavy borders.