So I bought the parts to build the DIY heater.
I used a rubber band, a smooth reducer (1.5 to 0.5 inches), and the 75W heater.
Next I put the rubber band underneath the lip of the temperature dial prior to siliconing.
Silicone was placed on the bottom of the heater, right at or above the water fill line.
I pushed the heater into the reducer and the rubber band gives a little space between the silicone and the temperature dial so that I can still turn it. I am gonna leave it overnight to dry and then I'll nick off the rubber band. This was exactly how the last build went but I tried to show this in more detail.
Right now the silicone is curing. Once it's all done, I will put the housing together