Just in case anyone has problems changing the width and height, replace all instances of #vis# with "#vis#" and #visdump# with "#visdump#" in autoconfig\program.ini as the double-quotes will allow spaces in your paths and be able to write values properly. Also to shorten the skin width, change either xconst (lower value=shorten, higher value=widen), or endsize. Changing both will shorten it too much. Not sure what either does but changing just one of these two worked for me. Change yconst to half your intended skin height (e.g. if you want the skin to be 100 pixels tall, change yconst = 50).
Is there a reason that this skin needs the beta release vs stable?