I have the same kind of cage. Its wood, with two vents, a front glass door, and no hole for a heat mat. I use both bulb and heat mat. I just place the zoomed UTH inside, on the wood.
Don't forget that wood viv's hold heat really well, so they get warm fast. My tanks approx. 30 gallons, and I have a UTH meant for a 10 gallon tank. Adding that with the 50 watt bulb is more than enough to keep it hot, and thats in a room that stays at a consistant 64 degrees.