If you find you haven't been able to get level, backing/ forwarding onto boards then one option is to place a bottle jack between the tandem wheels, under the FRAME, and jack the trailer up to allow you to place an additional board(s) under the wheels. This sounds extreme, but is actually not that difficult. I've had to do it once or twice. A pain in the butt, but doable.
I DO NOT recommend using bottle jacks to level or further stabilize the trailer. Level under your wheels only .... then use your stabilizers to minimize inside movement. You'll never get rid of the normal 'bounce.' It's not really noticeable until you're in bed and DW decides to go down the hall for a pit stop ... or vice verca .... but it's the norm.
Reasonably firm-up the stabilizers and that's all you can do! (IMHO)