A friend and I brewed an 8 gallon batch of russian imperial stout, split it between two primaries and added a 1.5 packs of safale 04 to each. The OG was 1.100 and after a month in the primaries it has stopped at 1.030. This seems a little high and we don't it to be too sweet. We've heard of guys adding champagne yeast in instances like this but we're worried about the gravity dropping too much. Advice?