Thing is the transmitter display apparently allows values <100 with up to two decimals. Even using values such as 38 instead of 3.8, I still loose the second decimal digit, which is important sometimes. I already have a bunch of ways of seeing the actual voltage (it´s and arducopter with a lipo alarm connected directly to battery+automatic warning on drone buzzer+warning on Ground Station). The thing is that it´s also interesting to see the actual value and the battery icon directly on the controller. The fs ia6b also supports voltage monitoring directly through the power supply; only problem is that the board´s limit is 8.4. That´s 4.2 volts short.
P.D.: I´m using a Pro Mini for this project. Should try changing a few things to see if it works.