I've used wall panel moulding ....
http://www.lowes.com/pd_494917-293-M...panel+moulding
to allow me to create channels that I can stick 1/8 inch thick plexiglass into to create divisions. I run 3 pieces of it, front, bottom, and back silicone into place. Use 100% rubberized silicone (same as aquarium silicone), a L- or T-square for straight level lines, and a sharpie. On the
outside of the tank, I measure out where I want the division and then with the L or T square I mark off the tank with the sharpie. I then line up the panel moulding and silicone into place. Allow 24-48 hours for it the cure, and about a week to off-gas the acetic acid (vinegar smell). Cut your plexi about 1/16-1/8 inch shorter than the inner dimensions and it should be easy to remove from the moulding for any type of cleaning.
Heating is simple, place the heat pad on the bottom, back, smack in the middle using the new division as your centering point. An appropriately sized heat pad (and proper thermostat to control it) for a 50/55 gallon tank should do fine for a divided tank.
As much as a lighting activist as I am, many colubrids are crepuscular during the warm months of the year and move to nocturnal during the hot months; some are even diurnal during the cooler warm months. HOWEVER, there is no need for a basking light with corns. Where I do advocate lighting, is just a simple fluorescent light as I feel this aids establishing/maintaining in any captive animal's (save maybe cave salamanders and Mariana Trench organisms) natural circadian rhythm. I may not have lights on all my cages in my herp room, but I've got enough light on enough timers to easily establish a day and night cycle.