I do not see any torque spec in the service manual for spools. They are not a Kawi part so I suppose there is no official spec. The torque spec for the front footpeg bolts is 18'lbs. I think that is about the same sized thread as the spool bung. 17 - 18'lbs seems about right to me. I doubt if there is much vibration in the swing arm so they should stay in fine. Just check them every few hundred miles to see if they come loose.
If i have not mentioned, the two screws on either side that hold the lower fairings down WILL come loose every 300 miles from exhaust vibration. You can tighten them pretty good because they screw into metal. Don't overdo it though, because they tighten against your plastic and that could crack. Check them often
..........and while I'm off the topic...
The rubber grommets or well-nuts as we like to call them, should not even be close to snug or you will damage the rubber. The slight tension of the rubber holds them in very well. I have never had one fall out. Absolutely do not over-tighten that one on the back point of the tank fairing. Let it be almost loose. It has a very long screw and it will not loosen up on you at all. I cracked the well-nut on this one and it scared the crap out me because the well-nut was hanging inside the airbox. It could have broken off and fallen in when I had to pull it out to replace it. If you went over your bike and tightened those 2 in real good, you better loosen them up. The hole they plug will cut into them if they expand too much from overtightening.