Hi Rune,
Scorpion Backup Guard (BG) works fine as such but has the drawbacks You have mentioned. I have used the BG for two years now, in MythoS 125E (two seasons) and in MythoS Pro (1,5 seasons). I use Master Mezon ESC with BEC in both (and Hacker A60-7XS, Q80 14-XS).
I was thinking about Emcotec DPS Micro SingleBat (F3A Edition) or the DPS Micro DualBat (F3A Edition):
SingleBat (for single battery):
http://shop.rc-electronic.com/DPSI-S...=A11064&p=3664
DualBat (for two batteries):
http://shop.rc-electronic.com/DPSI-S...r=A11057&p=541
It has electronic on/off switch controlled by an external magnet from outside. Drill a 5 mm hole in the fuselage for the LED and the DPSI Micro can be glued to the fuselage’s inner sidewall, then You will easily see when it is turned ON.
The DualBat can be used with one battery also, I asked Emcotec, but then You must use Y-Cable they said so You feed both connectors on the DualBat.
/Bo