I've tried some of those suckers on a 25 yr veh and found them severely wanting. I spilled 1 out of 5 gallons of gas.
After that I got an integrated metal funnel and outlet tube resulting in much less spillage.
With the price of gas these days, there is great incentive to have NO spillage.
I don't always have it with me, so the hack rides around in my brain taking up un-used space, just in case I should need it, and don't have the metal flex funnel handy.
Field expedient. Great concept to live by.
/johnny