is the number of spin flips per Skyrmion, $\sigma$ is the strength of the disorder potential and $A$ is a phenomenological parameter. The first two terms determine the optimal Skyrmion size in the absence of disorder.[@UKmodel_Allan] The form for the third term reflects the property that Skyrmions with smaller $K$ are smaller and will be able to concentrate more strongly close to the potential extrema. This simple model gives an estimate of the interaction strength at which $K > 0$ Skyrmions first become stable $$\gamma^*=\frac{A}{2K_0U/(e^2/\epsilon \ell)-\tilde{g}}\,.
\label{gammastar}$$ The parameters $U$ and $K_0$ can be estimated[@UKmodel_Allan] for filling factor $\nu=1.25$ as $U/(e^2/\epsilon \ell)\sim0.014$ and $K_0\sim 1$. Using our numerical result for where the transition occurs at $\tilde{g}=0.0018$, we estimate that $A\sim 0.1$. From this, one obtains an estimate of $\gamma^*\sim 7$ for the cross over point from conventional quasiparticles to Skyrmions at $\tilde{g}=0.015$. This is in reasonable agreement with the actual cross over point $\gamma^*\sim 10$ (see Fig. \[phase\_diag3\], the transition is out of scale in Fig. \[phasediag\]) given the simplicity of the model. These estimates of the maximum disorder strength at which Skyrmion physics is realized could be checked by performing NMR experiments in samples where electron density, and hence 