Is renaming 20-11 theme enough to protect it?

Hi,
I know that when customizing the core theme (twenty eleven in my case), I should create child theme, to prevent damage when updating WP. All I did was to copy the 20-11 files into differently named folder in content/themes and making all my changes there. Is this enough? I know this is not real child theme, but all I needed was to cut connection between WP update and my theme.

Thanks!