I did the first few runs on my Plett Extra 30-10 Evo with a spinner with the front cut off to leave around 3/4 dia. hole. It has a lightened backplate so the air gets through to the front of the motor. The problem is that this spinner even with the lightened backplate was much heavier than my ES Composites carbon one. To cut the front off you need a spinner without the central bolt and this is limiting. I have had a few flights with the uncut carbon cone which still has a lightened backplate and I couldn't measure any difference when temp gunning the motor hold down bolts from inside the fuz. They go into the hottest part of the motor and never got above 50deg C. The ambient wasn't much above 15-16 C when these tests were done so they need to be repeated when it warms up a bit round here.

Malcolm