Extended chords over major and minor scales

[Bob]

Similar to my other seventh chord posts.

If you have a major scale or a minor scale (melodic ascending/descending and then harmonic too I guess), what 9th chords would go over that?  What 11ths?  What 13ths? 

Maybe diatonic?  That seemed to work well with the seventh chords.

Although I've read you're not supposed to have clashing minor 9ths intervals because of the dissonance.  I think that happens with a iiim9th and somewhere with 11ths between the third and fourth step of the major scale.