In my opinion, 30% vs. 35% is probably going to give you a negligible change in starting reliability. I don’t think there’s any firm ‘line in the sand’ to say what will or won’t work. In other words, I’d say go with the mix you have.

Regarding the possibility of an explosion, some have banned the use of cell phones at gas stations here in Canada and the US for the same reason. Hypothetically, there is a ‘chance’ that a gas station could blow up when a cell phone rings but the likelihood is miniscule. In order to have an ignition, you need to have roughly the right air fuel mixture to sustain the combustion. I can't recall any instance of this ever happening...

In the case of a turbine, I’m sure some of it gets sucked into the turbine’s inlet and burnt but I really don’t think there’s anything to be concerned about. The amount of gaseous fuel stored in the hose should dissipate very quickly, to a point where it can't go off all of a sudden. In one case, I’ve seen a KJ-66 homebuilder do this with the ‘start-gas’ (propane in his case) connection right on the intake of the engine. With the engine idling, he disconnected the propane and vented it without ignition. He’s done it a few hundred times now... By far the more significant danger in that situation is keeping hardware or fingers out of the intake. In short, you probably don’t need to worry about it...

Kelly