Back when I wrote this thread I set up my cages the way it is pictures with 2 foot of 12" heat tape. Currently I use a single piece of 12" heat tape that is 4 feet long and run it longways accords the back half of the bottom of the cages. I would post some pictures but I don't have any currently.
As for which is better I'd say that depends on how the cage is setup. If the cage is going to be divided I would go with the 48" piece of 12" heat tape. If the cage is going to be for a single snake I would set it up as pictures in this thread.
I wouldn't use 2 pieces of heat tape side by side on a T8.