I had my factory monos re-arched at a truck spring (Wall NJ) place back around 2010. They had the factory specs, but I wanted the car a bit higher. So I had them set them at 1.5" over stock. They came out great (not cosmetically though
). Pretty sure they did some press work plus a little heating.
Still on those same springs today, they might have settled around 1/8" to 1/4" in all this time.