Quote Originally Posted by lord jackel View Post
No...as the wattage is different as is the resistance between the different sizes. If you were to do it you would overwhelm the 3" and most likely burn it up. Also, you wouldn't get consistent temps.

You need 1 thermostat per size of Flex...but you can run the same size in parallel without issue.

Hope this helps
Have you tried this before? I do it and it works fine here.. I have a few helixs running 11 and 4 inch tape.. temps are perfect....