I believe it's pretty difficult to not get gray glands using the LM. The trick is to, which I'm learning myself, and I've been using an LM for a very long time, I have the LM1 so I'm going on years, is to go in 20-minute increments, even though you may feel you can do more. Of course your body will let you know. The trick is to rest and massage after these increments. That will help tremendously, I'm going through a injury myself as we speak because I went on too long sessions using the LM, hanging. Rarely I have a hard time to get an erection after my length work, but if I can't it's no big deal, just wait a bit then I can get going for my erect stretches.
Very much appreciated for the info