Search YouTube for example of replacing slide toppers before you begin your project.
There's plenty of fabric there. If you can find an awning shop to cut a few inches off and resew the bead, you'll get away cheap. I did that a few years ago and they charged me $25 for 1/4 hour labor.
Be very careful handling that awning with the spring tension it's under. You may be able to put a pin in the shaft to keep it from turning while you work on it.
Don Ford
2004 Safari Trek 31SBD (F53/V10 20,500GVW)
'09 HHR 2LT or '97 Aerostar MiniVan (Remco driveshaft disconnect) for Towed vehicles
BlueOx Aventa II Towbar - ReadyBrake Inertia Brake System