dash,
First, congratulations on your gains. That is great.
>My question is will I continue to gain hanging 20 minutes at 20 lbs or do I really need to shift to a lower weight and more minutes in the day? <
I would not change a thing, until you are sure you have stopped gaining with whatever you are currently doing. This goes for anything.
Now, most guys do have to add more intensity, either in weight or time, as their units become stronger. You have already gone up a lot in weight. If you have the time to do so, it would probably be best to add a set(s). But do not drop your weight if you add a set. Start out at your normal max weihgt. Then, if because of fatigue, you have to lower the weight, that’s great.
Another thing; if you are limited in time, be sure you are using heat. That will help you out tremendously.
Bigger