Reasonable values for the $\gamma$ parameter:

$\gamma$

float[dimensionless scalar variable]

By default, we set $\gamma$ to the nominal value $\gamma = 1.75$ from the Turner energy rules and formerly from the original application of the JS model where $\gamma = 3/2$. When $\delta = 2$, this is exactly the same equation as the JS exapression. Deviating from that value is certainly not a crime, but with a little thought, one might realize that the effect from this contribution would be mainly to weight the entropy less or more depending on whether $\gamma < 1.75$ or $\gamma > 1.75$ respectively. The contribution from the second term in () is a constant, and the third term is usually neglectable for these problems (but not all problems). In many cases therefore, the result does not change dramatically when this parameter is changed.

In short, if you really desire to know what will happen, you are free, but consider also that that is why you are lost. Limits have been set such that $0.3 \le \gamma \le 4.0$, where values in the middle seem the most sensable.