A brief Google search yields a link to this German
forum. Apparently, the Bölkow Junior indeed doesn't have the most spacious cockpit of it's class. With regard to take-offs from grass strips, user Armin Mueller writes 'The only drawback is the somewhat lame take-off performance. 600 m of grass should better be available.' Thomas Endriss confirms 'As you have mentioned correctly, there are no short field take-off characteristics. I only go below 600 m of grass when there are no obstacles in the departure sector.'
There is a
manual on the website KeesM has found. It's in German, but you won't need a translator to read the take-off performance tables on page 43 of the PDF. In case you need one, I'd be happy to help.