As tech inspector it is your job to get compliance, not impose penalties. I would go to them and tell them what you know and that you are being pressured into action, so don't come with the C/M chassis if they don't want to be found illegal. That can't be anymore fair of you. There should be no hard feelings that way. The bad part is if you have to invest in something to catch them,it is deducted from the charity proceeds. If you don't, the race could belly up and their would be no proceeds for charity. Being the tech guy is a thankless job. Where a dummy gets disqualified for rounding off a port with a ball hone and a guy that knows shot peening and acid etching can make any port he wants. I actually got tore down 26 times with a restricted Yamaha KT100. It was so far away from the good end of port tolerance that the tech guys shook their head. The jug was a throw away in the machine shop. Factory port way to off for an unrestricted engine. It made power about 2,000 RPM lower than everyone else but it was good power curve.