If proceeding as pictured, better try it low and slow. When you load the figure eight side, the prusik is going to contact the limb and slip until the figure eight moves down and causes the prusik to reengage. Then when you load the prusik side the reverse will happen. I think you'll create a seesaw effect over the limb with potentially adverse effects not to mention loss of efficiency. Climbstihl's version, maybe with the twin ropes through a link to the butterfly and throw line to the link for retrieval would get my vote.