I made my own leaders from thick muslin and sewed the centre line on with my machine. I also sewed the 3/4 inch casing for my Leadergrips before attaching to the frame.
I found the Leadergrips very tight for when all three layers are snugged to the muslin, so I "stretched" a few of the pieces by clamping them to a length of dowelling that was a little larger diameter than the leadergrip. (Hope this makes sense). I keep these pieces separate to use for this application. I had extra pieces because the dealership I bought mine set at only stocked one size (12 foot) and I have a 10 foot frame. I love the Leadergrips, especially the flexibility of multiple pieces vs long lengths. It is important to start in the centre and work your way out to the sides when attaching fabric.
Enjoy the process and the learning!