switching keels

Ok, so i was really bored and put a marblehead class keel onto a Soling 1m. The boat is a rocket now. Much faster than the conventional 1m it races against. However, it seems to go sideways a lot when not going fast. Since the Marbleheads are much bigger than a Soling 1m, do they tend to suffer an excessive amount of leeway when not moving quickly? This Soling hybrid thing is a quick boat when its going forward, and sometimes it can be pretty fast sideways as well.