Organizations run race gas for consistency in testing, not because it’s necessarily required for the engines to run properly. Additive packages and ethanol content in pump gas isn’t consistent and that makes testing for compliance on pump gas nearly impossible.
That said, some classes where you can adjust timing on the engines to be really aggressive and still within the rules…will have the potential to cause detonation with pump gas if the timing is set this way. If the engine was built by a “builder” call them and ask their opinion.
When we ran Yamaha’s we ran pump gas pretty much exclusively in testing and the motors actually ran better on pump gas than they did on race gas. I’ve run a mix of pump and race gas in my KA100 as well without hurting anything. I’d guess you’d be ok, esp at an 80/20 mix but again, a quick call to a builder would probably put that question to rest for you with confidence.