unfortunately even the newest version of YARPP delivers no normal CSS-file. It´s always something like styles_thumbnails.css.php?width=120&height=120&ver=4.2.2
This way (as mentioned months ago) it is not possible to minify this CSS. I know you want to deliver those height and weights with this PHP-link, but for what price?
All other plugins are using normal CSS-links, nothing with PHP or so - and all those can be minified, which reduces HTTP requests and so on.
When will you change this?