How long are the carbon fibre rods for a Travelling Kossel?
Most information I was able to find was the arms are 80% the length of the horizontal structure.  I did find a copy of the original Google Sheets that everyone used a few years ago here.  The source of that link did mention that there may have been some issues with it but all of those links were dead ends.  

Some things to note:

The height doesn't matter, it has no relationship with the arms other than you are losing approximately the arm length from the height when figuring print area as some arms will approach vertical when reaching the outsides of your print area.

The arm length isn't terribly important from what I could find.  Longer arms = less travel of the carriages and possibly lower resolution.  Shorter arms = more travel of the carriages and possibly lower print speed due to required movement.