An interesting question has been raised. The stock cap is not vented and any of them back to the 02s could build up a vacuum and get hard to remove. What concerns me is finding out that Brents flush mount cap like I use (vented) doesn't fit the later models. If I remember my original stock cap was a fairly loose fit threading in. It was hard to remove sometimes due to not being vented but never where tools would be required.
If they have somehow screwed up the template of the tank neck and are making them smaller, the original cap might still fit while Brent's doesn't. If you combine the vacuum problem with tighter threading, I could see how it would be very hard to remove.
My question still is why in the heck would they intentionally change the thread diameter of the same tank that's been used since the beginning. I'm beginning to think there's a manufacturing screw up that caused this. Are the tanks still made in England? There should be a way to find out a clear answer.
