How much variance was common for the bonnet during 1810-1813? The beautiful example seems quite a bit longer in the brim than the image, although the image is 1806.
Thank you for this example and looking forward to more!

I too have made one of these bonnets, using the bonnet in this image, and another with a rounded brim as inspiration.

The rows of diagonal piping and rounded brim are what I particularly liked, and I also took the back row of piping round to join at the back, leaving a circlular opening for the gathered back piece, as the images show.

There was a very extensive array of options available in early C19th headwear. There are examples of bonnets with both longer and shorter brims, with the brim extending around the back of the head (as in the fashion plate and Sandi's reproduction), with curved corners or with square and with a shaped brim rather than the rectangular method I used here.
Dating these variations, even with the aid of fashion plates, is difficult due to the individual approaches taken by milliners. The specific precedent for this bonnet is in a fashion plate dated 1810 which is in the collection of the Museum of London. Unfortunately I couldn't get copyright clearance to use it here.

My decision to make this bonnet the way I did arose from looking at a very wide variety of images, but I could have chosen any of these options!