Here is what they did:
1. Place the solar panel on the canvas and mark the grommet holes on the canvas.
2. Glue a vinyl disk about 2 inches in diameter to the underside of the canvas at points where attaching bolts will be placed.
3. Puncture a hole in the fabric through the vinyl.
4. Place a 1 inch diameter or greater plastic or stainless fender washer on a 10-24 or similar stainless bolt and pass it through the canvas.
5. Place another fender washer on the bolt on top of the canvas and secure with a nut.
At this point, you have a reinforced canvas sandwiched between two fender washers.
6. Pass the bolt through the solar panel grommet and secure with an acorn nut.
7. Repeat for each solar panel grommet.
See diagram below for details.
On the installation shown above, the solar wires were run through the channel used to attach the canvas to the frame thus hiding most of the wiring.