Is there a formula for converting pancake batter to waffle batter? I have a wonderful pancake recipe that I would like to convert into a waffle recipe.  Is there a generally accepted formula for doing this?  Based on other recipes I've seen, it looks like the amount of oil is the main difference.  Would more flour or other ingredients need to be added to compensate for additional oil?  Are there any specific pitfalls to avoid?
Add an extra egg and 1/3 cup oil, my waffle recipe uses half baking powder, half baking soda while my pancakes only use baking powder (but when converting a mix I usually just do the egg and oil).