Plane terrain following in mountainous area with steep valleys

Any experience or ideas on how the plane would react in terrain following mode in a mountainous area with steep valleys? I would be doing surveys and want the plane to simply fly over these areas with minimal altitude decrease. Obviously, if it tried to follow the terrain too closely it would drop rapidly and then not be able to pull up in time and crash into the other side of the valley! Thanks!

Also, is it possible to view what a flight might look like using terrain following prior to actually flying it? This would enable identifying potential issues.

Thanks!