We investigate a coordinate-free model of flame fronts introduced by Frankel and Sivashinsky; this model has a parameter \alpha which relates to how unstable the front might be. We first prove shorttime well-posedness of the coordinate-free model for any value of \alpha > 0. We then argue that near the threshold \alpha \approx 1, the solution stays arbitrarily close to the solution of the weakly nonlinear Kuramoto-Sivashinsky equation, as long as the initial values are close.