Re: When is HENKA WAZA hunky-dori?
My experience has been that you can usually employ an adaptation if the "partner" you are training with is advanced enough in his/her training to safely accept the unexpected. With a beginner, however, there may be a safety issue, so it is better to let the instructor deal with any issues of resistance or hesitation. In a more advanced environment, the issue may be one of attitude, rather than ineptitude. A seamless transition to a more effective technique may only need to be done once or twice before the resistant uke decides to stop testing you. Then, if necessary, a polite suggestion like "We'd better stick to the program, so one of us doesn't end up injured..." will usually ensure that the point has sunk in. Don't turn it into a competitive thing, however, because some people ignore common sense when such competition arises.
I also have a friend who bows out for a "potty break" when this sort of thing pops up. She says that uke usually gets the message.