In SS3.24, discard only fleets are not treated any differently when doing the benchmark (reference point) and forecast calculations. This means that when SS is searching for F% and Fmsy, it scales the F for the discard fleet at the same time it is scaling all the other fleets. Some of the assessments in the U.S. Southeast have dealt with this by making adjustments in settings of forecast.ss, perhaps an example of this could be posted by someone who has experience doing this. In SS3.30, we have created a placeholder to deal with discard only fleets more explicitly and easily, but at this time it is a placeholder only.
Rick