I put in an order today . I will see if they will help with the spills. If the dont I will try welding in a washer type restricter in the tube. I have some extras on hand.
If it spills going around a corner it won't help with that (slow it down maybe but nit stop it.)
I'd get one of the caps from slantsix dan or one of the custom made ones made by a member on here. (can't remember the username offhand though) they do look nice, not original but nice just the same and it'll seal up the top opening just fine. if it blows back from filling it them the fillerneck mod works great. I've done 3 so far and they were a pita to do but did stop the kickback from the fuel nozzle spillage.