This type of thing should be easier in the forthcoming SS version 3.30, although I'm not sure about the options for blocks extending into forecasts.
In SS 3.24, I think the easiest approach would be to change the starter file to run the model starting at the estimated values in the .par file and then modify the .par file to change the values of the forecast recruitment deviations from 0 to positive or negative values. The forecast recdevs in the .par file are under a heading "Fcast_recruitments" but that vector also includes any "late" recdevs from the final years of the model that you may have separated out. Whatever you modify, should appear in the recdev column of the SPAWN_RECRUIT section of the Report file (read into r4ss as $recruit).
You could apply this same approach (and maybe already did so) to control the distribution of recruitment among areas.
