Too late, after purchase, I realized that the 3DR Power Unit is limited to maximum 18 volts input, corresponding to 4S LiPo… The internal voltage regulator is the limiting factor.
Well, in my project I will use 6S, that is like 27 volt at fully charged pack.
I did a simple hack, replacing the original switching regulator with a simple 7805 regulator (you might find it in Radio Schack or any other electronics shop).
The 7805 max Vin is 35 volts so 6S LiPo should not be a problem.
Be careful and exercise some patience when de-soldering the original regulator board from the main board, so you dont ruin the tiny surface mounted components on the main board. This does take some de-soldering experience…
Next step is to solder the 7805 regulator in Place. I found this one in a drawer already soldered to some wires, but you might just as well solder it directly on the mainboard. Make sure you turn it the correct way.
In the attached photo the gray wire is Vin, pink is ground, blue is 5v out.
In my project I am only after the sensor functionality, the module will not supply power to any processor board. If you intend to use this hack and use it to supply your processor board you might need to attach a little heat sink to the 7805.
You should also be aware that the hacked Vout is 5.0 volts.
The original was 5.3 volt, allowing for 0.3 volt drop over the Schottky diode protecting the processor board.
Disclaimer - so far this worked for me - but you do it on your own risk - don´t blame me if you ruin anything 
Enjoy!
/ Tomas
