If you're assuming you've got medium tension because you've never changed them, you might very well have light ones. They come in 10lb, 20, and 30 sets. I assumed the 20s were the default, so that's what I put in, but it was quite heavy compared to what mine was from factory. I can't imagine what a 30 would feel like, almost require an extension I bet.
So if that's the case, that I know of they don't go lighter than 10. For lighter, you might be best off with Sik's suggestion.
Wiley.