Yeah I wouldn't do it. A twist on cap wont hold the pressure a crimp crown cap will. And growlers are known for leaking out carbonation anyway. Typically growlers are only good for beer you plan to drink within a few days
there's a tons of threads on this. You have to realize that they are meant to hold already carbonated beer, NOT beer carbonating, where the pressure is built up the forces itself into solution. Some folks will say they have no problem, but others like above will say differently. To me, I sure as heck wouldn't want to play Russian Roulette with my beer.
Nor would I want to risk 30 bucks trying in a fancy growler either.