The aerodynamics of a towplane in a kiting glider situation

Just because one system is superior and safer to another has nothing to do with whether it is approved for installation by the FAA. The documentation for installing a tow release on a particular aircraft is clearly spelled out. If it permits a Schweizer hook, then that's what has to be installed to pass inspection. Changing to a Tost is not in compliance with the documentation, so it would not pass inspection.

Getting a Tost approved for retrofit to an aircraft for which it is not specifically approved can be an arduous and time consuming process. ANYTHING having to do with the regulatory environment at the FAA is a long and painful experience. Bob Carlton and I spent NINE YEARS getting the FAA to agree to a method to extend the life limit on the Pegasus. And that was an instance where the FAA had obviously made a mistake, violated their own procedures and the Administrative Procedures Act and still "circled the wagons' to defend the one guy who pushed the life limit AD through.

I am certainly not arguing that getting a Tost approved for all aircraft would be a desirable thing. It is just that EACH aircraft type would have to be individually approved. There are very few if any "blanket" approvals across aircraft types for mechanical devices. Avionics are another story, but we aren't talking about that type of equipment.

As far as releasing liability, the big question is whether the tow pilot or his employer (club or commercial) is providing an aviation service for compensation. If the glider pilot is paying for the tow, then it is fairly obvious. However, as you say, four lawyers can easily deliver six opinions.