Back to 4.1.2 from 4.3 with no problems

I am back at 4.1.2 after trying different 4.3 roms and I have my old speed and battery use back again :)

The only thing I need is Bluetooth 4.0 LE but that is only available in 4.3

Is there any thing I can do to make my Polar H7 heart rate working again with Android 4.1.2 ??

Thanks