I don't have Wyandotte bantams, but I do have bantams with large birds, and I have zero problems.
Now a really large rooster with a really small hen might be a problem. How large is he? Any idea of his weight?
I have the reverse situation: a tiny Sebright rooster with some large girls. He tries to mate with them, but isn't successful because the parts don't line up, and he has sometimes bloodied a comb or two. Tonight, he decided my Cochin was his lady. Why he chose one of the biggest girls I have, I don't know. The "heart" wants what the "heart" wants, I suppose.