Takumi's and Kazuma's bondage forms didn't look painful at all. Their legs were even closed the whole time, and their heads didn't snap back or disappear into the body or anything. >>

I imagine Agito's will be the last OW OW OW MIND RAPE form. Den-O's is just Momo, Kabuto is the Zecter (closed legs), and Hibiki's is a giant taiko stick (again closed legs).