Hello, some info to my construction, the thought behind it and some simple facts.
The low 3/16" exit copper tube has a reason! Copper is the best thermal conductor one can use (I could use silver if you are willing to pay for it).
The units I build are for hobby beek's, but I have many with guys doing 5,000 and more hives. They use about 1 for 500-1,000 hives.
Now, transmitting the 300 watt heat from the element to the bowl is one thing, but keeping the vapor tube hot is a different can of worms, but as much important as heating the bowl. I have tried larger diameter tubes, 1/4" for example, but did not get as nice of a vapor 'blast' as with the 3/16. My tube goes in close to the bottom and bends up along the back side of the entrance just to a level under the plug. This makes the dropped charge to be vaporized before it gets to the exit, vapor tube.
I noticed that the soft copper hardens over time with the 400-430°F and should not be bend much after 5-10 uses!
The InkBird ITC-106RH is much superior to the Mypin TA4. From factory setting, it does not over-shoot as much as the Mypin and automatically converts the C° to the correct F° and vise versa, so no resetting of the target temp. when changing from C to F. The PID holder is much better then the flimsy little clips on the mypin.
Here the bottom vapor tube with a Mypin TA4-SSR. Great to treat through the top lid with inspection hole.