The stab should be rock solid. No slop or movement at all.

The elevator, well, slop can come from the linkage, on either end, or be in the servo with sloppy gearing. If you want tight servo's, spend the money and get some expensive servos. Otherwise, live with what you get. Normally, though, they are pretty solid. That leaves the linkage. The only slop is in what you put in, for instance, using 4-40 size control horns with 2-56 linkage. Not likely. If you drill out holes in the control horns or the servo arms, you will get slop. Not much but visible.

This is the same for any servo linkage. Slop usually comes from sloppy building or over-drilling, or the use of the wrong hardware.

CGr.