In 2014 I went from a Sony 350 to the Aura 6". It was such a great thing, as small as my Sony but a bigger screen and a light. I loved it to pieces. Having more text on the screen was so much nicer, not to mention the light, which was handy on my commute.
When I bought my Aura One in 2016, I was smitten with the size from the very first moment. This was a surprise, I always thought I liked them small. It is the size of a book page and all of a sudden reading on a device was just like reading a book - only better.
I've kept my Aura 6" for as long as I've had the Aura One, as an out-and-about-device, but never again did I enjoy reading on it. It was just too small now.
The Forma has a different size, it is square and the not so book-page-sized screen wasn't for me. I switched to a Pocketbook Inkpad 3 Pro to get the 7.8" screen again. There is a Tolino, called Epos, that sits on the Aura One chassis, but it is a bit longer which makes it have a wider bezel at the bottom. I am not sure if I'd like it as much as the KA1, as it distributes the weight differently and is a bit heavier. The Pocketbook is a wide and long as the KA1 and weighs about the same, so it feels familiar. If there was a Kobo with a 7.8" screen available, I'd jump on it, as it is the perfect size for me and I like the Kobo software better than the Pocketbooks.
Yesterday I went into town to take a look at the Libra in its Tolino drag. Nice reader, the smooth plastic feels better to me than the rubber of the Forma, but it is too small and has that weird form factor, too.
So, for me, there is no going back ever to a smaller screen. I guess I'd easier adapt to the square size than to a smaller screen after three years of owning a bigger reader.
I think you'll love it too.