Originally Posted by DiapDealer
Your trouble is exactly what calibre's output profile and/or font scaling feature is all about.
Maybe you are right, I tried to believe and do as you suggest, but I could not get the font-size of 0.8em in the body tag after a conversion, no matter how I change the profile or base font-size.
I set the font-size to 0.8em in the body tag before a conversion, but it goes to 1em after the conversion. (My profiles are both default ones.)