The only full biography of Hofer that I know of is
Kidd Hofer -- Last of the Screwball Aces, by Troy White. It may have what you want. Troy's website is
http://www.starduststudios.com/kidd-...ball-aces.html
He is now located in Australia, and suggests that people in Europe contact him for the price with shipping.
Enjoy!
Frank.