I suggest that you start out with the Basic Tack Fuse Firing Schedule suggested in our Fusing Basics video. You can vary the process temperature based on how much texture you want in your result. Watch the free video here: https://videos.bullseyeglass.com/videos/fusing-basics/
The diameter of your piece should not affect the firing schedule too much, unless your piece is very close to the kiln elements. The variation in the thickness of the piece is important to consider, and the variation in thickness is accounted for in the suggested Basic Tack Fuse Firing Schedule shown in the video.
I hope this helps!