Leopard gecko question?

i have a baby leopard gecko he is in a 20 gallon tank. i have an UTH that stays on 24 hrs/day and is supposed to be for a 15 or 10 gallon tank. the UTH is right below his warm hide where he usually stays. its below the tank and reptile carpet and its not actually in the tank (the people said to put it there and i read it needs to be 1/4" away from the gecko) is this warm enough? i also use a regular lamp and lightbulb that i use about 12 hrs during the day. i am going to get a thermometer. but if its not warm enough i really dont wanna go buy another UTH but could i get a red infarred heating lightbulb to raise the temperature a few degrees? if anything i feel as if the warm side is at most only a couple degrees cooler than it should be. so will the red bulb heat it up to where it needs to be? thanks!