We present observations on electrohydrodynamic instabilities in materials for which the Helfrich parameter ζ2 is strongly temperature dependent. For ζ2 decreasing to one, the threshold voltage of the conduction regime diverges, and both dielectric and conduction regimes disappear for ζ2 = 1, as predicted by the theoretical models. For ζ2 < 1, we still observe instabilities, which are interpreted in terms of amplificated twist fluctuations. Such an amplification can occur for positive values of the friction coefficient α3, and electrical conductivities ratio σ||/σ⊥ smaller than one