Thank you for your input.
Actually maybe inversion boots a bit too much for me too. As I mention in the past, I had neck injury as a child and now after using gravity boots my neck did not like it much. Sometimes I hear not very pleasent noise then I turn my neck, and also just a slight pain.
So I stop hanging myself for a while untill my neck will be OK again. I did not expected this. I thought it is not big deal to hang up side down, but looks like it is too much when you had injury, like I had.
Doctors told me that my neck never will be healthy again, but they told me that exercises will make it better, I thought gravity boots will make it better. Now I think that, it could be a little too much for beginer as me so I will take it easy.