Yeah, F1 doesn’t do anything for me either. But I was able to fix it by modifying the retroarch.cfg file. You can either do this globablly for all retroarch cores or make a cfg specific to the core you want to change and then use the –appendconfig to include it (for examples of this see the es_systems.cfg file).
The value I changed was the following:
# A floating point value for video aspect ratio (width / height).
# If this is not set, aspect ratio is assumed to be automatic.
# Behavior then is defined by video_aspect_ratio_auto.
# video_aspect_ratio =
You can uncomment it and pick a value like 1.175, which looks pretty good to me. This value was taken from here: http://forums.nesdev.com/viewtopic.php?t=8063