1 GCD with huton down isn't a big deal, since inputting the mudras and animating the skill before you can use a GCD is a bit more than 2.5s

what affects how much time you have for huton after your 2nd raiton just depends on if you're casting your ninjutsu on CD or not really. if you aren't, any wasted time is ticking against your huton; that's all.