So I need to raise the temperature on my cool side but I want to try to avoid lights if possable. Right now in my 40 Gallon tank I am using

http://www.amazon.com/Repti-Therm-Un...9740277&sr=8-2

This does not cover half of my tank.

Would it be ok to use

http://www.amazon.com/Repti-Therm-Un...9740277&sr=8-6

That way it is larger and will help to heat the cool side more?