The tk's 6000 and 9000 are 5/5 head heavy and the jjs are 4/5. There's a major difference in swing weight only if we're talking about the same weight class for both models (3u or 4u). The swing weight of 4U Tk6000 is identical with 3U JJS.
Just get my Tk9000 3UG5 last night, strung with BG66 at 27lbs. Btw my tk9000 is krp code version. I compared Jetspeed 8 with normal MYC(Malayisa) code and KRP code, and i felt krp code is far more solid than normal version. According to my seller, the recommended tension suggest by victor is 28lbs, but krp code will enable us to string up to 35lbs. Hitting time, when i clear birdie from backcourt, i felt so weird as i couldn't clear to opposite backcourt. I'm not really sure about that, then i switch back to my VTZF and it was fine. The 3/5 stiffness is a joke as i felt the shaft stiffness is almost similar to my VTZF 3U. So yesterday for the whole night i couldnt clear well at all (compare to my VTZF). However, surprisingly the smashes were fine, at least i am not disappointed with that. Due to limited time constraint, i only manage to test out 1 and half hour. I think if this is a normal version of tk9000 might be fine for me, i would try it out on next week once i get back from my trip. If it still doesnt work, then i will lower down my tension to 24lbs.
I've tested my TK9000 3U KRP for a 2 hour game last week. It is less stiff than VTZF and lighter in the head than VT80. A good pick for people who fancy head-heavy racket yet dislike the stiff VTZF and head-heavier VT80.