Sitting on a "Tush-cush" wedge cushion

I have a wedge shaped cushion that I used to use it when while driving, to help ensure my hips are higher than my knees, and alleviate pain in my sacrum/low back.  It's called the "car-tush", but I think they make a bigger one called the Tush-Cush "http://www.tushcush.com/product_info.php?products_id=66" .  It's about 16" wide, 13"deep, and almost 3" thick on the wide (rear) edge.  I just discovered that it fits perfectly on my office chair, and it seems to promote pelvic anteversion.  I have it set up now on my officeI have a wedge shaped cushion that I used to use it when while driving, to help ensure my hips are higher than my knees, and alleviate pain in my sacrum/low back.  It's called the "car-tush", but I think they make a bigger one called the Tush-Cush