What type of heat cable are you considering?
something like this maybe?...
"Big Apples flexible heat rope"
Revolutionize the heating for your reptiles with the hottest new heating product... Flexible Heat Rope.
This breakthrough heating product is perfect for anywhere heating is needed but has the added feature of being flexible so it can be wrapped around any object, placed behind your cage's false wall or under a false floor.
The list of uses for Flexible Heat Rope is endless but the best feature is it's completely WATERPROOF.
This means you can use it in your outside enclosures or high humidity situations.
Say goodbye to blown bulbs as Big Apple's Flexible Heat Rope is built with high quality components to delivery years of heating.
Flexible Heat Rope is affordable, efficient and completely safe.
Flexible Heat Rope runs hot so a thermostat or rheostat must be used with this product.
This is especially true in situations where the reptile can actually touch the product...
http://www.bigappleherp.com/Reptile_Supplies/Product/Big_Apples_Flexible_Heat_Rope_119500.html
Is anybody currently using this product? Can it be cut to length?
Flex Watt has an ultra thin physique of just .012 inches thick and it's element is sealed in a tough flexible plastic ...
...the tape can be cut to any length for use on a single cage or even a row of cages.
...be sure to use a rheostat or thermostat to control the tape's heat level.
http://www.cornsnakes.com/forums/showthread.php?s=&threadid=4892&highlight=racks+flexwatt
http://www.cornsnakes.com/forums/showthread.php?s=&threadid=6027&highlight=racks+flexwatt
The flex-watt would be a good logical rack design choice...

Bite the bullet and spend the dough for the flexwatt, properly installed, it will last many, many moons. imho.
P.S., With either product, be sure one uses a rheostat or thermostat to control the tape's heat level. Otherwise "baked Snake" can result.
http://www.cornsnakes.com/forums/showthread.php?s=&threadid=6137&highlight=proportional
