Donald,
Yes, more strands and knots will make a stronger hanger that will hold the pot more securely. With 3 or 4 vertical strands, I've had a problem with the pots getting lopsided and tipping out one side. Yours may be better balanced.
If you can hang your pot upside down and knot the strands around it as you go, you'll get a custom fit. Much easier than trying to use a formula based on the pot size, although I'll bet there is a math whiz on this site who could draw it out with circumferences and radials.
To make the strands detachable, look at S hooks (the kind with one closed end) at the big box stores. That's also a good place to look at various cords and ropes.
