Thanks for the answers. I was intentionally a little vague on my question.
Without admitting violation, a person that I know very well went flying in a C172 the other day in a winter location. There had been a lot of frost accumulation but fortunately for the pilot, there were wing covers on the aircraft. However, they did not prevent most of the bottom of the wing from being covered in thin but clearly visible frost. As well, there was not cover on the tail which had frost on both sides of the horizontal stab.
The frost was removed from the tail due to concerns about lift but the wing is quite large and it would take a seriously long time to clean the bottom of the wing. The instructor wasn't concerned about the frost on the bottom of the wing and the pilot agreed to go flying but mentioned that he would rotate at a higher than normal speed at a lesser than normal rotation rate and climb out at a higher than normal airspeed.
Keep in mind that the wing on a C-172 is quite high lift as compared to some other aircraft where one might not want to attempt this sort of thing. As well, the takeoff weight was well below maximum and the OAT was well below freezing allowing for better than normal performance, Everything went fine and a check of the wing after a few minutes in cruise showed that all frost was gone.
I was just curious if there is any performance penalty for a situation like this?