He and Knapp were the very definition of great technique and leverage. Neither guy is a big man (both are around 290), but they did the job, and did it quite well.
In Knapp's case, he has more room to grow, and could add another 10-15 lbs without losing speed. In Wagner's case, he may very well be maxed out on his size.
That's not a killer for a pro career, though, since there are pro-style systems where smaller guys who have great technique and leverage, can thrive. The Erhardt-Perkins and West Coast systems would be great for him.