Make sure you pin from the center out too. They say pin a fist apart.
A large size quilt is hard even for those of us that have done a few before. I actually start from the top right and work a section down and then up again and do it that way. You will always have a bunch of fabric to the left and seems on your lap so the larger your table the better to help support it all. One piece of advice was to try to concentrate on just one area with your quilting. So I do a small area - like 10 x 10 inches that would be in the middle of my spread out hands and then try to rebunch the fabric and concentrate on the next area. I also use the machine gloves that helps to grip the fabric. Some people that might not have them use garden gloves.
Good luck and do make sure you take some breaks. That's alot of concentrating!

Hugs,