Tagalog nang

[potet]

"I don't quite appreciate -- yet -- the nuances of J-P G Potet's points, so
I will
not respond to them in this post." Resty CENA

nang X replaceable by sa X-ng Vs nang Y not replaceable by *sa Y-ng

I understand your caution because this is one of the fundamental principles
of  Tagalog syntax; it is not a matter of nuance. :-) Either one proves the
demonstration is false or accept it; there is no middle way.
Resty, I think your valuable explanations belong more to the field of style
than of that of syntax.
 Best
Jean-Paul G. POTET