I've tried a number of things to reduce trailer movement while on site and stabilizers down. From X-chocks to lock the tires from any movement, to complete replacement of the OEM jacks to HD scissor jacks and stronger C-jacks like the originals. The scissor jacks lifted easily, but wiggled more, and did not collapse as nice as the OEM's.
Once I found the manufacture of all these types of jacks, I stumbled on another offering of theirs...locking arms! One box contains 2 arms, and when installed (VERY SIMPLE) the trailer is solid as a freaking rock. They will work with the C-jacks found on the Visa and Vista line, no need to replace them.
I'm not sure if this is the best upgrade I've done, or the maxfan. I love them both!
http://norcoind.com/bal/products/index.shtml