We noticed a fair amount of shake in our new-to-us 2012 Rockwood Ultra-Lite 2701SS. Enough that I considered a new bumper sticker:
If the trailer's rockin'
Don't let it stop you knockin'
Nothing inside's shockin'
It's prob'ly someone walkin'
Couldn't find one, though, so instead I ordered a pair of
Valterra 020106 RV Stabilizers. I had seen mixed reviews but since they were portable and under USD 100 for the pair they were a lot cheaper and easier to try out than alternatives such as SteadyFast or JT Strongarms.
Our situation may be unique - the previous owners had some sort of frame reinforcement done at the rear of the trailer, so that's where I put the rear stabilizer (instead of under the rear bumper as suggested).
My wife and I tested it, one taking a turn on the bed while the other walked up and down and side to side. The difference was remarkable... it's hard to quantify but I estimate that 80% of the trailer shake is gone.
We put the other one under the stairs.
It wasn't much additional help in the walk'n'rock department, but it did completely eliminate the springboard effect felt in the trailer when someone enters or exits.
We're very pleased with the purchase.