There often seem to be many who worry about 'musical form'......"is it true Sonata form?".........."that's not a Concerto, there's no cadenza" .....and so on. I'm not too sure that Schoenberg or Messien worried to much about form or indeed that they should have done. To me you write what you feel, using the skills and knowledge you've got, never mind what mathematical equation it adheres too.
What do you think?????
I've just added a Concerto on my site.....(with no third movt cadenza incidentally).....and would welcome any feedback.