Don't expect them to actually "stabilize". You may end up experiencing what is often called "bounce", "shimmy" or simply "movement" when set up at a site. Bounce does not bother some and some don't like it at all. The degree of bounce will depend on a few factors like the TT GVW, it's length and strength of the frame. Lippert elec. stab. jack (the most common out there) has significant inherent flex in it's various components and it's just the way they are.
You may very well find yourself wanting to add stabilizing braces like the Bal Lock Arm in the photo. (There are a few other manufacturers of a similar product) A screw or bottle jack at each of the 4 corners of the TT plus ahead of the wheels may be desirable also and will minimize the vertical component of movememnt. X-chocks work very well in minimizing fore/aft movement as opposed to ones under the tires.
While not very exotic or sexy looking, the basic scissor jacks work very well in conjunction with Bal Lock Arm (or other) cross bracing.
The electric stab. jacks are not intended for levelling a TT. You should level it first before extending the legs down.
We still like our elec. stab. jacks though and wouldn't be without them. I have one set of the BAL braces to install at the rear of the TT once the weather improves enough.
