I had XM make me a custom leash of my own design. It is 12ft stretched out. 4 feet behind the leg is coiled. The coil is about one foot long. This leaves only 8 feet of straight leash making drag in the water. I think its the perfect leash and XM should put it in production.
I tried a full coil leash. It knotted whenever the coil dragged in the water. Bad idea for surfing. OK for cruising only.
I also tried a calf leash. It worked fine provided you never paddle on your knees. Going to my knees allowed the cuff to cut a hole in my leg. Ouch!