I am in a round robin that just started in our local area. I just finished the first round on the center I recieved. We will exchange them at our meeting each month. We have 6 in our groups. Our rules are kind of spelled out. The first round had to be pieced triangle of some kind. Round two is set the block on point. Round 3 will be a border with curves, round 4 is our choice, round 5 is applique. I think I like your idea of no rules for each border. Our center was to be 12 to 18 inches. It could be pieced or just a cut of fabric. The one I submitted is pieced and 16 1/2". The 1st one I recieved is a cut piece of fabric. Borders must be 3 to 6 inches finished. I would love to join this group. having major surgery on Thursday to reconstruct my right shoulder. Four hour surgery. Dr says I will be in brace/harness for 6 to 8 weeks and then 6 to 12 months of therapy. Just not sure how much I will be able to do. I asure everyone my first goal is to rotary cut, sew, and quilt! Oh we also put in our bag a small sprial for each person to write what they did and why and a disposable camera so each step could be photographed. I am going to scan all the pics and notes onto photo fabric and use that as my label.
Hope this gives you some ideas.
Connie