Quote Originally Posted by Argentra View Post
I think I can answer that: Since hatchlings live in such small tubs, belly heat would most likely upset the gradient and not allow for a cool side. Therefore, back heat is used to still give a warm side but not overheat the entire tub.

At least, that's my take on it from what I've heard.

EDIT: Geez you guys type fast!! An entire page while I was writing this!
Let me address this if I can.

1) You want to create a basking area for your reptile, not a hot plate to sit on. I like to have the tape cover no more than roughly 1/3 of the floor surface area when it is used for belly heat. This will provide your animals with a nice thermal gradient so they can decide how warm they need to be.
In most small to medium shoe and sweater boxes the 3 inch or 4 inch tape will do the job. Unless your room temperature is unusually cool you should get good results. For larger sweater or blanket box applications you would probably go with the 11" wide tape.
These are quotes directly from Rich at Reptile Basics. This is an acknowledged expert in the field of safely heating snake enclosures. The Flexwatt FAQ page can be found here:

http://www.reptilebasics.com/Flexwatt-FAQ-sp-4.html

Now let's do some math. I have in front of me a Sterlite #1851 6qt/5.7 L hatchling box. The measurement of the bottom of this particular tub is exactly 11 and 3/4 inches (that's actual interior measurement). Now using 3" flexwatt (the recommended one for belly heat for a hatchling box) you easily have what is recommended - that being approximately 1/3 of your snake's "floorspace" heated with at least 2/3 available off heat.

That flexwatt again must be controlled by a tstat or very carefully monitored rheostat but that's good common sense and the recommendation of Rich at Reptile Basics.

This is what I do, what I know - not what I've read or heard - take that for what it's worth.