If it does crack, guess what? Pay $10 at your local exhaust shop and have it rewelded. Bolt it back on and you're done.
I'm concerned that you removed the flex joint and I didn't see any support bracket for it. The stock turbo outpipe is supported just before the toilet bowl, not far from the turbo outlet. Isn't this like putting a big lever on the turbo and putting pressure on it every time the engine moves. Almost all the modded turbo "downpipes" I've seen on here lately are doing this. Putting the stress relieving toilet bowl or flex section far from the turbo, changing the dynamics of how the engine moves in relation to the exhaust pipe. These things are art and I hate mentioning what I see as flaws but in my mind I see these things trying to move the exhaust several inches, on the end of a big lever ... and the turbo is supporting it all. Trying to imagine them, even at idle, makes me wonder where they will crack and how long it will take.