We also have the 2955RL and we do the following....
Above are the 3 items I use to stabilize my rig. In my opinion, leave any one out of the picture and the other 2 are questionable.
The tripod of course goes under the pin box and it is adjustable. For me the tripod by itself was useless until I added the chocks and the jacks.
The chocks are mechanically tightened between the tires and unlike the cheap plastic wedge shaped chocks, affectively remove all back and forth movement.
2 jacks go under the frame just behind the rear spring shackles. They are snugly cranked up against the frame but not enough to lift the trailer. I didn't feel I needed them but a second pair of jacks can also be used in front of the shackles.
This system along with the rigs front jacks and rear stabilizers take nearly 90% of any movement out of my rig.
I should note that I only use the above when I will be in the campground for a week or more but I always use the mechanical chocks.
After I have the rig parked where I want the chocks are the first things to be put on and when breaking down the last things to be removed.