I haven't added pop-in vents yet. If anyone has tried these cans before and after, I'd sure like to hear impressions.
Another big surprise for me is that I actually
like the way the valve mechanism is activated.

I thought I'd hate it. The pressure of the snout's hook against the lip of the fuel tank's mouth opens the valve. Pulling back slightly on the can to relieve the weight instantly stops the flow. No more overfilling, and I've been using these newer cans for several months now.
I'll add pop-vents if it makes much difference. My only reluctance is concern about swarf from the twist drill ending up in the cans, even if I drill upside down. Only one of my tractors has a filter basket inside the lip of the tank opening. For the other two, it would be hard to use a filter funnel and still activate the can's valve mechanism. Does anyone happen to know if the swarf will float in the diesel or gas once the can is refilled? If so, filtering it out right away would be fairly easy.