I think I understand what the plan is. I just cant tell how the joists are fixed to the studs or rafters (having a hard time with the perspective). All I can see are the metal plates that, I assume, are just reinforcements. So then I am asking how are they fixed tot their crossmembers? If they are strong enough to support the weight then my next thought is how long of a span is that? If it’s several feet then I would not want to center it on the joists. The final question is “after unstallation, what if someone were to hang on it? Would it still hold?” I’m kinda imagining you’re looking to install a heavy bag.