I haven't heard enough positive reports of the king pin stabilizers to invest in one.
What I did do was had a JT StrongArms knock off installed on my fiver by the dealer. If I had to do it over again, I'd likely go with the SteadyFast system. I like their marketing material the best. :)
After that, I do use a good quality between-the-wheel chock. I have only ever used it, so I don't know if it really makes a big difference.
Otherwise, we have a *lot* of movement still.
I tried a Valterra Stabilizer Stand cross-wise in front of the axles that seemed to do *no* good. I might try relocating it, we'll see.
My next step is to get scissor jacks and put them just ahead of the axles. I've heard a lot of reports that they make a big difference.
My full write up about my stabilization experience and attempts is here:
http://www.learntorv.com/2013/06/shake-shake-shake-rv-stabilization.html