I know making your own is more fun, but if you need quick, safe and functional, I can recommend a ready made bridle from The Marine Superstore in Port Solent or your local supplier. Price was £10-15 (sorry can't remember exactly) and the main attraction was the red pulley frame is bouyant.
IMHO it would be very hard to foul a prop with this bridle since it won't go over the flange above the prop on my motor. As always though, nothing stopping you fouling the tow rope!
P.S. This bridle has towed a 2.5 metre dia. inflatable with 3 adult men on board at 20 knots. So no worries about quality. (mind you they were more like quivering kids when they got off