OK, thanks for the input. Sounds like a blender is a negative snap from a vertical down-line aileron roll. If held it results in an inverted flat spin. I have never entered a spin in that fashion. I always enter a flat spin from a power off full stall, nose drops, aileron roll, then add rudder, elevator, and throttle to flatten for upright or inverted. I'm sure if you did a blender with any appreciable air speed it would severely stress the fuselage behind the main wings.

Anyone else with input please chime in.