I just received my 2013 AHRMA Handbook. Under section 3.3 Technical Inspection sub section 3.3.2 it states that Snell M2010 helmet are required for ONLY road racing and dirt track. All MX, PVMX and Cross Country must meet Snell M2005 or equivalent standard.
So in those respects you are good to go. Unfortunately, you modified your helmet and in the same section it also states that ALL helmets will be closely inspected for ANY damage OR modifications to the shell and inner liner. Any damage or modifications (to include non-OEM visors) to the helmet found will be grounds for immediate denial or disqualification from any AHRMA event.
...just kidding about that last part