1sq ft per ft of snake. so... 6ft snake (which your carpet will reach in all likely-hood) means 6sq ft of floor space and because they can be semi arboreal would make it someone tall from there. In my experience jungles are not as arboreal as... say irian jayas, but they can all vary.

also, belly heat is always better for snakes. Lights right on the cage dry out the air and can stress out nocturnal snakes (even if they have a hide). ambient temp mid to low 80's, hot spot right above the heat pad or undertank heater should be high 80's low 90's. humidity 70% but can be lower and should be allowed to dry out from time to time.

that's a small enclosure for and adult but it would be fine for smaller/younger snakes.

I have wto Jungle Carpets and I keep both in their own cage which is 4 feet long 2 feet deep and 2 feet tall, and they use every bit of it.

Depends on the size of the snake. Also, male or female could make a difference also.  For a jungle, I would suggest 3x2 for an adult male and 4x2 for an adult female. 

I use 4x2x2 for both a male and female jungle carpet, then female is at least a foot bigger then the male but I see the Male use the space much more often then I see the Female use it. Plus I would rather go slightly bigger with a cage size for a snake anyway

i have several carpet pythons and most are in 332 vision cages or 4x2x2 cages. radiant heat works well if you have a shelf or limbs big enough for them to bask on but i also use flex watt on the bottom for belly heat. i also use  a rack system for some of my smaller males. it works great.