Ball Python in 40 gallon long tank?/Gerbils and snake in same room?

[Homebody]

Do you guys agree that it is too narrow, or do you think it would work?

I think that it's too narrow for an adult ball python for the reasons you mentioned.

For any of you that use tubs, what is the size/dimensions that you have?

When I started, I kept my adult male ball python in this tub (https://www.target.com/p/underbed-la...40#lnk=sametab). I upgraded to a 3x2x2 plywood enclosure because he repeatedly injured himself trying to push his way out. So, I wouldn't recommend it. If your going to keep him in a tub, give careful thought as to how you are going to heat it. RHPs, CHEs, DHPs and other heat bulbs won't work. I used a heatmat to create a basking spot, but I had trouble keeping his ambient temps high enough.

Because tubs don't have screen tops, you don't have to worry about heat and humidity escaping that way, but will it escape others ways (through the sides)? I guess what I'm trying to ask is in general do tubs hold heat and humidity better? Do you have to worry as much about humidity getting too low in a tub?

Tubs hold humidity well because airflow is limited. I suppose they hold heat as well, but they can't hold heat that isn't in there in the first place, and your options for heating it are limited. Most people that use tubs keep them in rooms with high ambient temps (75-80F). That's higher than comfortable for most people.