In print, I use a typeface with marked serifs for dentals and an austerely sanserif one for alveolars.
Emeneau demonstrated that this palatalization could also be blocked by a following alveolar in Tamil-Malayalam, but not in Telugu.
However, a critical problem, and the one relevant here, concerns the two contrasting taps, "dental" /r/ and alveolar /r/.
3) The alveolar tap /r/ seemed to be just that, a single quick tap on the alveolar ridge [r].
This is clearly a surface rule since in deep phonology alveolar /1/ functions as [-high].