Im back with an update.My own fault as expected - I had used a test pitch of 30 deg even though that was not the actual pitch.Tried again with the actual pitch (measured using the pitch tool) which...

Hi,I have tried this for a 30 deg roof so used 30 deg sloped area from the top and then 30 deg sloped area from elevation and the result areas are hugely different.Im not sure what Im doing wrong?