Thanks for the additional information about the feel of the device. I would also like to point out some limitations of firmware updates that might not be obvious to those who don't have a working knowledge of electronics. While the firmware can address issues and update functions, such as adding dynamic wattage adjustments and changing display items, they can not expand the output limits of the device. The specifications of the device at 5 volts (stated on the website) and 3 amps (calculated from the max wattage specs) is a hardware limitation put in place to keep the device within the safety parameters.
FYI: Based on the stated specifications, you will need to run a 1.7 ohm atty to achieve the 15 watt maximum.
While we have no way of knowing the physical limits of the hardware. It is very likely the 5v limit is set because of the use of Li-Ion protected batteries. Single battery mods that can run over 5v require high drain batteries.
Not a problem for me since I never go much over 4v with the 1.5 ohm RBA's I use.