1st question, what you towing?
our experiance is with fun flys and EPP combats.
line about 4M with an elastic band in the middle to take the tugs. you put a 160 degree bent hook on the nose, on TOP of the glider and the other end under the fun fly on the CofG ( guide tube on the tail helps, we used a film canaster with the bottom removed.
you take off, the glider pilot keeps down in to stay below the plane, when you want to release, the plane slows, and the glider dives away.
easy.
anything more than that....... i donts knows
Cubs are good + POWER