Mine are installed at the bottom. As I recall that is what the instructions stated. Been 6 yrs since I installed them.
In addition, when setting up you need to put pressure on them after you tighten the T handles. Tighten the T handles and then lower the jacks just enough to put pressure on the struts. If you can rattle the struts by shaking them by hand they are doing no good.
For the rear struts I crank the stabilizers until the rear of the trailer rises just a little, tighten the T handles, and crank the stabilizer back just enough to put pressure on the strut.
