Yeah, I’ve seen that guy before. He certainly can sling his punches though his physique might belie the fact. One thing - that’s one of those water filled heavy bags, which might exaggerate the power of the punches in visual and audio terms - but the guy still looks like he can hit very hard all the same.
He KO'd a 300 pound man in 1 round weighing 160. While that guy was a debutant he KO'd a real 260 pound opponent while weighing 170 in 2 rounds. Dunkhorsts went the distance 3 times with Armstrong(the tallest HW of the era) and went 22 with Ruhlin so his chin wasn't paper mache either. These 2 fights were 8 years apart too. Whether he'd be able to hit them or deal with their reachs is a whole different matter. Most of his fight weights aren't available but pure power wise i think thats enough.