I think JT65-HF is a constant amplitude (unlike PSK31) with phase continuous changes in frequency so it probably wouldn't matter if you were driving it hard enough to produce ALC. I don't think that would distort the signal. That said, it's intended for low power so if you've generating ALC then you're probably running too much power but... I guess it depends on the radio and how its ALC works. I've had some fun with JT65-HF. It seems to be a popular mode in South Africa for some reason.