I have tried two types of prop adapters on my Sportster and don't have a lot of confidence in either method.
I haven't flown the plane yet but I am almost afraid to.
Which method is best? The collet or the set screw?
It seems that, since the set screw is tightening down on a smooth shaft, there isn't really that much to grab on to.
The set screw adapter came loose tonight when I accidently reversed the prop direction on my TX.
Prop came flying off and I started thinking that might happen when I am flying.
I was wondering if I put a groove in the motor shaft where the set screws hit, wouldn't that give it a better chance of staying on?
Do you have to really, really tighten down the collet to get it to hold on to the shaft?
It also came off when I was testing the motor.
I can't be the only one that has a problem with these things (or can I?).
I'm new at this and need some advice from all you experts out there.

I prefer the collet type myself. Collet type adapters automatically center themselves on the shaft of the motor or gearbox, plus they grip the entire shaft, not just one spot. Set screw types can sometimes "push" themselves off-center, and they only grip at one point. I have yet to have a collet type come off.

What you don't want to do is "noodle-arm" it when tightening anything related to the prop. The general rule of thumb is, "If it flies off, you didn't tighten it down enough."

The rule of thumb can be compromised by a poor-quality adapter, or a damaged adapter of course.

I haven't used a prop adaptor yet, but I guess it would go with the territory to make sure you clean the motor shaft and the adapter as best you can before putting it on.

i use tyhe collet type myself..and grind down the side of the motor shaft a bit to flatten it..then put the adapter on,,and have never had 1 come off..