Zerif-Lite: Background image size

Hi I’ve read a few posts regarding Zerif Lite Background image size, but no-one seems to have gotten to the bottom of it. Firstly the documentation size is way too big by about 3 x, and secondly, when you do get an image that vaugely fits, it is not responsive and looks terrible on other devices. Did anyone get to the bottom of this? I thought maybe it’s a locked down PRO feature, but I just checked and the documentation says it’s all fully responsive on the the lite version too. Thanks. http://www.ginagarvey.com