Maxsurf Motions Peak Enhancement Factor

I'd like to know which wave spectrum should be more appropriate for seakeeping analyses in the Mediterranean sea.

While screening through the web I found some publications which are proposing different gamma values (peak enhancement factor) for the JONSWAP or the Bretschneider spectra.

I'm wondering if there is any chance to adjust this parameter in Motions in order to modify the spectra as desired.

Thanks

M