if you can make half the tank about 83 to 88 degrees and the other half about 73 to 76 degrees then it won't matter. If it heats the entire tank and does not give you a cool spot, then you might have to do something different.
Not knowing the dimensions of your tank or the pad I could suggest to you that you only place half the pad under the tank and then wrap the other half of the pad up the side of the tank. If you're using a thermostat this method will work nicely. I used to heat a Boa Constrictors cage the same way and it was fine.