RE: crow braking
I would certainley NOT recommend any flyer of ourexpensive jet models to check your CG postion by entering a spin on the first few flights and most pilots would not be happy doing this.
As most of our jet models use either a semi or near semitrical aerofoil section longitudinal dihedral or "decalage" as is correctly named is very small 0-1-2 deg positive max. so only has a small effect on inverted trim. Flat bottom wing sections such as Clark Y require more decalage for neutral trim in normal flight.
Much safer to roll invered at a good height and check how much down elevator you need to fly level.
If the models CG is too far back (not a good idea) you will notice a pitch up in trim straight away.
Phil.