For now, until the new software allows you to select random girls, the only way I've found to do this is to use the small size with a number of girls playing at once. If a girl or clip appears that you don't want to watch right now, left click and drop her off the bottom of your screen and a new clip or girl should replace her. Then when you DO see a clip you want to watch, right click and select large size.
Personally, I actually like this way of doing things! Rather than randomly nudging a new girl onto our screens as we used to do, you can now choose between a number of clips that are visible at the same time:) To me, this is an improvement! Thanks Totem :D