Ease into this carefully. Don't over extend your expenses at this time. Instead of making 8 of one size perhaps make 16. Beating the size demand is impossible.
Customers are very nice people.
Hope this helps. I make childrens clothing in about 6 different sizes and 12 fabric choices. Since I sew on allready made denim overalls etc. I don't feel I can increase my inventory enough by myself since I am also out selling a couple days a week. You are right that customers have a hard time choosing which they like best, but then there is also the customer that has to have a certain one.