Not sure why you say that "The RV-12iS POH also has no reference to a KIAS Vne, the only Vne number is 136 KTAS." That is incorrect. Below is a screenshot of page 2-3 of the RV-12iS POH, Rev 7.
BTW, I spent my professional career in flutter, aeroelasticity, and aeroservoelasticity; as an engineer, DER, AR, manager, etc. So I know a little bit about flutter (and loads!).
Oh yea, I'm done here.