I'm getting the 24x18x12 (about 22 gallons) soon and I was wondering what size under tank heater I should get. My other tank isn't as wide so it was easy to pick. I'm thinking of the UltraTherm 17x11. This would cover the whole right side where I would have my warm hide and moist hide. And it would be about half of the tank. Most people recommend 1/3 of the tank and I was wondering if 1/2 was ok?