When there are right angles, nesting the seams would be helpful, but when they come together at different angles, it's possible that nesting is counterproductive. They will be crossing each other in such a way that the extra bulk is going to amount to 6 layers for a tiny distance, and that's enough to work against you. You could try ironing the seams open. Then drop a pin straight up and down at the points where the seams meet (not the edge, of course). Then try using little clips or pins to the right and left of the seam before removing the pin that's straight up and down. Good luck!