Not a pro on PE issues but follow what @huge-girth just said, focus on length first, that's what I am doing with my hanging sessions. I don't have as much time as u do so i try to hang 30mins morning and 30mins at night, hopefully I would get some more time soon enough, as for your target of 1 inch per month,I really don't think that's posssible, if it is you could end up adding an extra 12 inch by the end of the year ( 1 inch by 12 months) and you probably wouldnt be able to use that anyway.
Aiming for a inch a month keeps me motivated and hard working which will give me faster results even though I might not get that inch in a month I gain as fast as I can. So if I would have set my goal to 1cm a month which is more realistic I would be putting less work in it, kind of psychological lol idk I was always on the extrem side of things. Even if I gain less than half of it I will not be discouraged, I will just have to work harder and smarter ? We all know its not a marathon and time is needed, Im just driven at this moment to achieve my desired length and girth no matter what.