In a multi fat(oil) recipe, every fat is playing a role in the quality of the lather. The OP's recipe is fairly high in palmitic and stearic fatty acids (>30) which results in lather that leans creamy (and bars that last a long time because they don't dissolve quickly). Increasing the percentage of oleic at the expense of a bit of the palmitic and stearic fatty acids would help the soap dissolve more easily which would lead to more bubbles.