I think that is a very cute stroller!! Very handy bein a stroller, carrier, and car seat all in one!!!
Sorry...dont know about the harness thing. You would probably jsut have to see how/where the hook up is inside of it as to what type of harness will be best. As for sturdy..if a harness dress holds when walking it should do fine with her just sittin in a stroller.
Goodluck! and be sure to post some pics of your lil girl in her new stroller when you get it!!!
