Mad Scientists Son #3-rule breaking

Today I pushed ahead into a section that may or may not work. I'm adding a new POV in the last third of my novel. You aren't supposed to do that. I can remember an instructor I worked with at Vermont College telling me that it was a bad idea when I did it in a manuscript I wrote over ten years ago. She was right then. The ghost of her voice comes back to me now.
"Don't do it. Bad idea," her ghost voice says.
"But it feels like it might be a good one."
"Same thing Napoleon probably said right before he invaded Russia and we know how that turned out."

She's right. I know it goes against a very sensible fiction writing rule. Do not bring a narrator in so late. The reader doesn't have time to warm to them. It's jarring also to have the sudden switch. It may undermine established rhythms you've worked for.

There are many good reasons not to do what I seem to be doing anyway.

Sometimes you just have to go with what feels right though. However, I am aware that I might be fooling myself so I'm going to keep this POV for now, but I'm going to be suspicious of it. In later drafts when I'm thinking about structure and I'm forcing myself to get some distance from the work, I'll try to be sure this actually fits and works. If not, I will be merciless. It will be gone faster than a bad piece of fruit.