I also use 2, 2000 CR250 AirBoot mounting Rings installed on the boot (I do not cut the boot at all), You can see from the last picture in this post. I put one ring in between the 2 rubber flaps and the other ring in the normal place. This gives me a much firmer mounting area. I am sending my mocked up airbox plate to LoudMouth MX to have a custom one machined out of Billet aluminum.
I have tested this on both my 2012 CRF250R Project and also on my existing 2009 CRF450 conversion, it works on both... But remember this is a 250 2-Stroke Motor in my GEN 5, not a 500 Motor..



