Thorsen is mentioned a bit in the Arnold unauthorised biography Fantastic.
Six and half feet tall and 330 pounds
A passage from the book
At the premiere, various luminaries praised Commando as a milestone in the history of cinema in which Arnold's greatness was immortalized. It was not the truth, but it was pleasant to the ear and nothing more than Hollywood's standard garish hyperbole. When all major players had their say, Arnold called up Thorsen to say a few words. Sven had just moved to Los Angeles and had never been to a premiere. He thought of it as nothing but a big friendly party for his buddy Arnold. "Yeah it's a great movie," Thorsen said, relishing the moment. "Congratulations! But let's be honest. Isn't it only a seven?"
Afterward, Arnold got his friend alone. "Sven, what the fuck is wrong with you?" He asked.
"what do you mean?" Sven said. I was honest
Yeah but you know this is the movie business