Another I recently came up with are these little rings above. They are cheap to buy (from office supplies shops and the like) and they fit just right on top of the bobbin as you can see in the photo. You can add one, or two, or as many as you like until you get the tension the way that suits you. And you can replace them easily when they wear out. Simple.
Now of course for someone who likes Aeros, I had to try the Pop-a-Bobbin shuttle. Very nice, well made (though still a little thick for my liking), lovely to handle. And it's very pleasant to tat "silently". But I do have tension problems with them. I don't know if there are tiny variations in the thickness of bobbins but some work fine whilst others practically "free-wheel"! Again, the little paper rings came to the rescue.
Also after seeing Fox's, I was then brave enough to change the hook on mine too. I have two and changed the hook on both. Really happy with them now as I wasn't getting on very well with the hook that was on them originally.
Now I hope I don't appear too critical of the Pop-a-Bobbin as it really is a lovely shuttle and I think it's great there are people out there who are making all these beautiful shuttles for us to enjoy.