Rather easy stabilize job?

sorry for this new thread … got another one started with a similar issue … though my approach has change a little… : )
what i’m trying to accomplish is to lock down a certain area i’ve tracked… i’m only interested in getting rid of x translation …so x translation and maximum smoothing are checked …odd thing is my tracking area is still moving … besides that i additionally wanted to use “centre” to get my area of interest pinned down in the middle of the screen…didn’t work either …when i checked “centre” my tracked shape jumped to the right margin of the screen…
any ideas…?
p.s. to get my track done i added necessary keyframes manually and set “link to track” to none … so the movement of the tracking shape is a rather linear one from keyframe to keyframe…

Can you show some screens to illustrate the problem? It’s hard to gather from your description.
What does the grid/surface do?