This one is only 20 row tall you should look at the other one, it curves even more. I am using the 1mm string, but it's also how I string it. I string it super tightly, and tie it off every time I reach the bottom. Most importantly when you reach the top bead, don't just turn around and go straight back down. Feed the string thru another two or three of the top edge beads, then go back down thru those beads and string the next downward row, and pull everything as tightly as you can the whole way thru. If you need more help or clarification, send me a message and I'll try and help.