You cant address the scroll bars in hippotizer to scroll up and down media with midi. I would drag a media select window out onto the pin board and use the + and - icons to help you see more or less clips.
Have you tried using notes and tags to quickly search you media? search the 4.3.2 manual for notes and tags.
Hmm, if you were to drag the mediaselect pin from a layer you are not using to the pin board, you could use a midi controller to select a clip on the layer and you would see the mediaselect window track the media that is currently selected. That will do it!