After all this time, my group is looking at getting back into CotCT; and we still haven't found the answer, so - has there been any clear answer as to what the prerequisite for Shingle Runner is?
Is it the Acrobatic feat, or is it ranks in Acrobatics? And if the latter, then how many ranks?
Considering that Shingle Runner is a straight-up better version of Acrobatic I'd have to assume that the feat is the prerequisite.
Your GM (or if you are the GM you) can look at Trinia Sabor's feat line, and see that she has the Acrobatic feat and the Shingle Runner feat and easily come to the conclusion its just a typo that they added an "s" to the feat prerequisite.