Nothing wrong with IMC in an unstabilised single IF the pilot is properly trained AND maintains currency at the skill (done routinely by the military) BUT BUT BUT - it's illegal in a civvy registered heli in the UK. The danger with showing a R22 pilot how to fly on instruments will always be that he/she may be tempted to push the weather limits a little further that is safe (although I do understand the good intentions of exposing a pilot to IF to give him a fighting chance if he should go inadvertent entry into cloud). By all means practice the skill with an instructor, but when the weather turns marginal, always chicken out early AND remember 'Don't Press On - land On'.