Which type of [s] do you use, the tongue tip up (coronal-alveolar) or the tip down…

Which type of [s] do you use, the tongue tip up
(coronal-alveolar) or the tip down (predorsal-alveolar)? Say a few words with
[s] and note the position of your tongue. Try producing both types of [s]
productions.

Some clinicians use only the tongue
tip down version of [s] to remediate [s] difficulties. Why might this be the
[s] production of choice if the child produces [_] as a substitution and
always goes back to this sound if you try to achieve a coronal-alveolar [s]
production?