I just stumbled into this thread and I had some experience with flippy caps'
I'm more careful with my STIHL flippy caps AFTER a all at once SURPRISE in the deep woods, the flippy cap came off and dumped fuel down my crotch and leg on a hot day when crotch cranking the saw immediately after re-fueling. Lots of burning and chafing later.
I thinking about taking a spare set of pants when I'm going to use my flippy cap Stihls.
I'll check into the convert