I installed manual scissor style jacks in the middle on my 31 foot Springdale. I REALLY tried to make it work for about 6 years, but finally gave up and just used the original 4 the last couple years we had the trailer. Here's why.
I could always get 4 of the 6 snug, but the other two were always loose. No matter what combination I attempted, or order of tightening, I always ended up with at least one jack not snug. So finally I gave up. Did it help the shake in the camper. No, not really.
Now, I have a 35 foot trailer, and with the 4 jacks only, I have very little movement. I really don't know why the two trailers are so different, but definitely much happier with our current trailer.
I have been in trailers where the owners used JT Strongarms on their (5th wheel), and it was rock solid. It was amazing.
I've learned to accept the wiggle now. Don't even notice it any more. Sometimes at night when the wind blows real hard and the trailer wiggles a little, it reminds me of the two Carnival Cruises we went on, and laying in bed, you could sometimes feel the movement of the ship. Very good memory there, so I've learned to enjoy the wiggle now.
