Did you measure an original cap, or a reproduction? How do you know the reproduction was accurate?
You lengthened the top so the cap would "look cool" - did any cap manufacturer actually do that? Were their ideas of what "looks cool" the same as yours?
Were real caps made from blanket wool and felt, or something thinner and lighter?
When I started in the hobby, I bought gear from the same suppliers as everyone else in my unit. My first forage cap was a fairly cheap one, with a thick leather bill and stiff sweatband. It was the right size, but I was never really comfortable wearing it.
A couple years later I was visiting a friend who belonged to a unit which put more emphasis on "authentic" gear. He let me try on one of his caps. As soon as it was on my head, I understood the difference. This wasn't a costume cap, made to be as cheap as possible. Instead, it felt like a quality piece of headgear. The materials were much lighter, finer quality, and more pliable. It didn't squeeze my head, it conformed to it. Of course that meant the materials were more expensive as well.
Hats, caps and footgear are some of the most difficult things to get right. If you want to try making your own gear, start with shirts and drawers, then move on to vests, trousers, jackets, and coats. Things like sleeping caps are OK but if you value accuracy, military headgear is best left to the professionals.