RE: Low C-rate with 1st flights after winter??
With preheated packs at 40 deg C the Voltage drop is much lover than with packs at room temperature. At 11 deg C the Voltage drop under load can be dramatic (down to 3,3V/cell)
In the new Hacker catalog on the page 42 is given the graph for the heated and not heated cells. From there everything should be clear.
@ Malcom H If your combo is making "squeals" it means that it is on the limit of the motor load and you should prop down. Latest generation of batteries is giving much higher Voltage under load which directly reflects into higher Amps and revs (~500 for a 20" prop) further increasing the load on the motor.
Velco