Radiant Heat panels are the way to go.
If you haven't already read this I suggest that you do:
http://ball-pythons.net/forums/showt...With-Pictures!
AS for Substrate I use Corrugated wrap. it looks better than newspaper but is just as easy to clean.
*Not my Image*
[IMG][/IMG]
Whatever you use it needs to be as thin as possible no thicker than 1/2". (unless you ditch the Flexwatt and just use a radiant Heat Panel)
Also to the other people posting an this thread the Animal Plastics T8 is not a rack. it is a 48" x 24" x 12" PVC cage