It's 30% to get the plans, and 50% to actually craft the plans. It's anytime, not specifically before Chapter 8.
Rom best support.
Also, it's possible. You'll need to 50% one, then the other, then the next, until you've 50%'d them all.
Of course, it's impossible to 50% them all at the same time, but it's possible one at a time.
In short, grind at the coliseum for shares.