Wordpress: Switching to Child-Theme

I had made a minor tweak to this site's .css file, and today I decided to move that tweak into a child-theme, so that it would "stick" after updating the main theme.

The instructions boil down to:

• Create a folder wp-content/themes/twentyeleven-child on the server (I am using the twentyeleven theme)
• Create a style.css file
• Copy/paste the necessary css-lines from Wordpress, and modify the appropriate lines.
• Add custom css at the bottom of the file
• Switch to Child Theme in WordPress settings, under "Appearance -> Themes".

Problem: Now all my previous settings of the main theme (which I had made under "Appearance -> Customize" were gone! They weren't really gone though, they were just "unset". I had to go into "Appearance -> Customize" again and redo the following:

• Old header image is gone: Choose it again, it's still among the uploaded files
• Old menus are gone: Choose them again in the "Navigation" subpanel
• Header text was displayed: I had to unset this again

I'm sure there are good reasons why these settings don't automatically carry over to a child-theme. Still, it's a bit of a surprise to do this "super-easy-can't-break-anything" procedure and then have to wade through settings again...

For future reference, this is what my child-theme looks like: A single style.css file in a twentyeleven-child folder:

/*
 Theme Name:   Twenty Eleven Child
 Theme URI:    http://hoeckerson.de/notes/
 Description:  Twenty Eleven Child Theme for minor tweaks
 Author:       Hoeckerson
 Author URI:   http://hoeckerson.de
 Template:     twentyeleven
 Version:      1.0.0
 Tags:         tweaks
 Text Domain:  twenty-eleven-child
*/


@import url("../twentyeleven/style.css");


/* =Theme customization starts here
-------------------------------------------------------------- */

#lookmabezier {
    width: 50px;
    height: 50px;
    margin: 50px; 50px;
    background-color: #88F;
    line-height: 50px;
    text-align: center;
    transition-property: transform;
    transition-duration: 0.5s;
    transition-timing-function: cubic-bezier(0.85, 0, 0.15, 1);
    transition-delay: 0s;
}

#bezier-demo-container:hover #lookmabezier {
    transform: translateX(200px);
    transition-property: transform;
    transition-duration: 0.5s;
    transition-timing-function: cubic-bezier(0.85, 0, 0.15, 1);
    transition-delay: 0s;
}