Thanks, this question has been on my mind as well. Since I do a lot of stop-and-go in the city while commuting, I'm constantly having to bang through the gears, so moving to a 15t seems like the best solution. I will go ahead and order the parts based on your threads and videos.The X300 puts out 39 (ish) horsepower. I had a very long discussion with a Technical Staff member at J.T.Sprockets and covered the concern of the thinner JT565 series sprocket compared to the stock. (5.8mm wide instead of 9.3mm wide for OEM). As that is a difference. The staff member assured me that the X300 is not a concern as the JT565 sprockets are factory on bike up to a full liter bike (1000cc). The shaft and sprockets are hardened and with correct installation to assure no movement at all there is no way the X300 bike will have any effect using the thinner sprocket. I've had my JT565 sprocket on my bike to 1/2 season = over 2000 miles and no issues at all. The X300 is nowhere near the limit of the parts. I was assured of this from a very knowledgeable J.T. Sprocket technical (engineer actually) person.
Great work, thank you.