I looked at these a while ago although didn't know what they were called. I was trying to emulate one of dave mead's horse bows which use bamboo limbs also. No idea of exact dimensions but starting at about 5cm or 2" tapering to 1cm 3/8" would be my guess, if you can get the bamboo that wide have an experiment and let us know (I have only been able to obtain 4cm 1 1/2" wide moso).
I'm putting the finishing touches on my 6th bow, but when I first started getting interested in this I think I'd planned to build about 20 or so in my mind before I'd finished the first, thinking of where to get the materials etc... I realised that I needed to stop over thinking it and just build something. If I make mistakes (which I do all the time) I try to not make them again. I can mess up ash boards and bamboo flooring bows and I will gain some experience for when I do start work on some osage or ipe
In case I'm being too subtle, I'm saying if I were you I'd finish your first (if your like me you'll probably want to do that again) once you've built something your happy with (like you I'm just starting out, still not made anything I'm happy with, proud of but not happy with) then think about expanding your horizons.