I couldn't see anyone running down the path attached to a balloon in that shot, then I realised you can't see the sky in that picture :0)
I expect a whole team of "supporters" to follow me with cameras waiting for a balloon incident of some kind. Anyway I have figured out how to best attach the balloon - attach it to another runner!
Like putting 'kick me' signs on people. Hmm, maybe someone will want to carry it for you, some 4 hour runners may want to share the honour.
Keep that balloon right away from me - I will run far enough behind just to sight you. I think you should attach several helium balloons and just float above us!!