The general consensus is as long as it doesn't impact anyone per se. But as it goes, each con has their own rules about such huge props, so I would suggest going with what's allowable for the most strict con.
As someone who has walked with huge wings (6' closed; 16' open) from conventions as small as Anime World Chicago and as big as Anime Expo, I'd recommend look for groups that are at least 3 people shoulder to shoulder and walk behind them. You don't have to be a member of the group, they just have to act as your bulldozer and plow through the crowd a path for you. If you're unable to find groups of three walking shoulder to shoulder, two will suffice, you just have to walk sideways close enough to them.
Now for photos, people are usually nice enough to give someone with a huge prop, specifically wings, a lot of room for photos. Walls are usually the best place since you can be there for long period of time and not bother people. But if you must, the floor is still very doable, just gotta stake out your spot quickly.
Still, you should come up with a way to quickly remove the prop from your body quickly enough in case of emergency.
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