Quote Originally Posted by anendeloflorien View Post
I'd think it would depend on how you're planning to run it. If you're doing belly heat I would go with 11" for sure. I have 4" on my RBI racks and that makes for a nice toasty warm spot plus gets the cool side up to a decent temp. It's mounted 3" from the back of tub and works extremely well. If you were doing back heat 17" might work but you'd run the risk of maxing out your thermostat depending on what you're using.
One helix could run 4 of my adult racks, thats 6ft of flexwatt per rack, 120 watts per rack, 480 watts per 4 racks, and THAT wouldn't max out the helix. This guys only talking about building one rack. Unless he plans to use one of those crappy A-life thermostats, I think he's in the clear.