The full hana uses an 18650. Since you won't be using over 20watts, you can use a higher capacity than the sony's available in 2100mAh and 30Amp continuous rating. It is slightly larger. There are side by side pictures on their website and some
reviews.
Vaporshark is 1100mAh.. and 22mm atomizers hang over the side.
The protovapor has a mini and full like the hana, but I think the hana is the only one other than the zen with a removable 18mm battery. The zen has 350, 500(or490?), and 650 tubes for different
batteries. I could only use the 650 since I'll be above 20watts most of the time.. and I think that looks weird.
I don't know what you mean by the math and regulation. Ohms law? Regulation gives consistent voltage all the way through the battery's charge (with the better
mods), from using a boost regulator that pulls more current from battery to give you that constant voltage.
That's weird a 2ohm atomizer is hot for you... I'm not sure about voltage drop on reo, but that's only about 8watts on a full battery. With electrical transmission, higher voltages are used instead of higher currents in transmission lines due to the amount of voltage loss from the heat in using higher currents. I need to brush up on my subatomic and electrical theory, but wattage is work, not necessarily just heat.. can't explain it more specific than that.. I couldn't go back to school this year on account of a newborn in September.