There is no perfect situation to please all drivers/riders and no way for the fuel vendor to bring every possible variety of fuel for every motors liking.
I would say for "Gas Class".. we just all buy the gas from the on site vendor.
The vendor should have at least 4 to 5 choices of event gas.
1 or 2 choices of lower octane unleaded gas (like 100 or 101) with and without o2 ?
and 2 or 3 Choices of leaded race gas 104, 110, 116 etc...
I know many cars/bikes that Drive in to race ask the question... "How do we drain the tank"
Do as Joe T says,,, plan ahead,,, so as to arrive at the track with as little as possible in the tank,,, buy your race fuel from our vendor,,,, and run... if you set a record and there is a gas protest,,, we will check the fuel,,,,
If all you had in the tank when you arrived was pump gas,,, and then added vendor gas to it,,, you "should be legal" if your tank had "a special secret in it" then oh well you may be illegal..
It is easy to comply with the rules...all of us using what the vendor has is a level field,,, I am not a fan of bringing "sealed cans of gas"... because it is differant than the "event gas"
But heck,,, I am not going worry about what others do... we all have trust and integrity and the ECTA and it's all for fun,,, oh yeah,,, some bragging. LOL
Charles