I've got a few Japanese books on the subject but the main one is 'Japanese Military uniforms 1841-1929' and I think it's published by a company called Kaiga.
Also, the new Foundry book has info in it as well.
They were about 600mm square for the cavalry and 1000mm x 800mm for the infantry. The rays should be 16 but they could be anywhere from eight to 18.
Hope this helps
cheers
James