I use painters tape on the back of my belts, it keeps them from distorting
Off the top of my head, I think I'm using a 21 needle and yes I am using the standard shuttle hook. You just have to play with the tension for a while, but if you can get it set properly you can sew about any thickness with minimal adjustment. I have sewn with 69 thread on my cobra and have had no problems or skipped stitches.