Haha first off- thank you. For me, DIY, scrapbooking, graphic design... It's all very soothing and fun to me. I just really love it! For the sandals- yes the string I used is elastic. I used clear so you can't see it. I found it right in the beading aisle at Michaels. It was long enough for me to make 4 pair with plenty left over. Sizing- I really lucked out on this. My foot is about a 6.5/7 and I know my girls have similar sized feet. Similar enough anyway. If i were you I'd use your foot as a guide and then for the 9's just make the string of beads that connects the anklet to the toe loop slightly longer. Better to have them a little snug. Since they are elastic they will stretch. If they are too long they flop over and don't look so good. I made my first pair too big and had to start over. They seem a tad fragile but not bad. My 18 month old got ahold of one and was pulling on it and trying to put it on and it survived so I'd say all in all they are pretty sturdy lol