I’m not really knowledgeable with some of the science of baking but maybe trying a different fat in your recipe? I read an article while back comparing using butter vs oil vs shortening (and I think there was one more item they tried). Some of the cakes turned out more light and some turned out more dense. I wish I could remember which ingredient did which! But it might be worth looking into? If I come across it again I will post it for sure!
-- Nikki, So Cal, www.Facebook.com/nikkibelleperchecakes