IME lots of boys like the idea, but have a low tolerance for loss of control, and no confidence that even if worked up gently they would actually enjoy being pushed.

Aye to the tolerance, but I think that is a HEAVY trust issue more than anything else. They’re coming to someone they’ve basically never met before, and you think completely giving up control is going to be okay? That’s how folks get murdered (statistically rare, sure, but can you imagine a better scenario for killing someone?) in every bad fiction novel and ‘true crime’ talkyrecording.