Beersmith does not have a "continuous hopping" option. So, what Peter suggested to you is really the only way to "simulate" a continuous program. If your IBUs are still high, then you will have to reduce the amount of each addition. There just isn't any other way with the software today.

Peter, did you raise your "OG" to account for the additional sugar added when calculating final ABV? I know its rather obvious and I don't ask to be insulting...but, we've all had that "Doh!" moment a time or two. What were your gravity readings before and after adding each sugar addition? And what was your actual OG before fermentaion?