Not possible to set default style of FormulaControl in app?

I'm trying to set a default style for `FormulaControl` in my entire app. At the moment it doesn't work, and I believe it might be related to this SO answer:
https://stackoverflow.com/a/39364416/4351604

If i'm correct, this should be added to `FormulaControl.cs`
```
static MyControl()
{
DefaultStyleKeyProperty.OverrideMetadata(
typeof(FormulaControl),
new FrameworkPropertyMetadata(typeof(FormulaControl)));
}
```