Samurai should be able to hold I wanna say about 5 Stacks.
My reasoning is because on a certain point in your double midare, you have press shoha then tsubame midare really fast so you don't hold the GCD for too long and clip, also makeing sure you don't forget and don't overfill on the shoha stack.
Its kinda clunky the way it is now and extra stacks will fix it.