I'll tell you one thing, I rewatched the third Charles/Layne fight the other night and was so unimpressed with both of them ... Layne looked like a smaller Tex Cobb and Charles had no legs and spent the night throwing one punch at a time and wresting with him ..
Layne was a spoiler in my opinion. He made fights ugly with his aggressive, mauling style. I don't think that would work with the 270 pound Carnera, but Layne's right hand might hurt Primo at some point if he gets careless. Layne had a decent jab but was open for the jab himself. Carnera would likely outpoint him with the left.