Advice on convincing my wife

I am seeking advice from women from their perspective on how to convince my wife to try another man. I think she likes the idea of it but says things won’t be the same afterwards if we actually went through with it. It drives me crazy. She is open minded and knows I watch cuckold type porn. She finds Black men attractive and is comfortable discussing it, but that’s it. She is also intimidated by big penises saying that it will hurt. I think she is just happy for it to stay as a fantasy.