Consider grinding a 6” for the telescope you have. That should be doable in about 40 hours of work. You would not need to build the rest of the scope because you already have it. Pay particular attention to control of the focal length.

I suggest that you get two identical 8” blanks. Using a plate glass tool and a Pyrex blank is asking for trouble. They will not grind at the same rate when using the same tool and same grit. They may not be the same thickness and their thermal properties will not be the same. There is much to learn by completing a 6” before making your plans for your Bino.

I was in the same position a few years ago when I wanted to build a 12.5” Newt. I first completed a Pyrex 6” F/9 and learned much about telescopes. It was a thrill the first time I focused it on the Moon. As I was viewing the ISS transited the moon. This was my first light with my 6” and that feeling can never be replaced by any other scope.

With that scope complete I completely redesigned my 12.5”. I have learned many things that I would not have known just be reading books and forums. Now I have a solid design for my 12.5”. This time I went with Fused Silica 12.5” F/4.5. I am working on the parabola at this time. I have not worked on it for several months due to a new job, a new house and issues at work but I am building the scope so that it will be available for my star test.

Good luck with your project!