I've been using a 150 watt Heat lamp to do my heating for Hera and I have seen so many people recommend UTHs. Well I have several questions before I go and consider getting one.

How do you know what size to get? I can guess that you would only want it to cover 1/2 to 1/3 of the tank since having it cover the entire tank will give to heat gradient. Is that about right?

How safe are they? I have heard that if done improperly they can seriously burn the snake, is this a common occurrence and how do you prevent it?

What type to get? I have seen something called Flexwatt mentioned a few times, is that a UTH or something else? Will it work for tanks or is more suited for rack setups? Are there any particular brands to stay away from?

How do you control the temps it generates? I have seen people mention that you need a thermostat or a rheostat with them to control the temps. How does that work? Do any UTHs come with them?

And lastly how is a UTH with humidity? I know that BPs benefit more from belly heat but will using a UTH increase or decrease humidity?

Sorry for the flood of questions, but I trust you guys' judgment more than me just blindly searching around on the net.