well i've made up a little something. as the bar went down to 12mm so soon after the 14mm plug i took a 12mm mild steel bar and filed down one end. I then cut a thread so that it could screw into the barkbuster endcap plug.
i weighed the two together and it only come out at 290 grams while the OE weight is around 490 grams (nearly half a kilo!!) - no wonder the xt's are so heavy.
anyway i've only done one side to see if it works or not - plus the garage was getting cold!