For my Bailey, I went to the clearance section back of the Joann Fabrics store and found this neat home decor or canvas type material at only $5.00/yard. I bought what was left. I made the leaders using the dimensions given in the booklet that came with the Grace Majestic Frame. I have enough left over to make another set of leaders at 45 inches wide perfect for a child's lap quilt. I stitched a quick fusible bias tape (1/4 inch) down the center of each leader. You can use what you have on hand...twill tape, narrow woven ribbon, etc. I do not see the need for the inches to be marked down on the leaders as long as you have the center marked on each leader.
For my previous shortarm set up, I used pillow ticking which worked well, too.