I read the OP's note as indicating that the rim walls were being pushed outward by the higher pressure. If this spreading of the rim walls is significant I'd certainly stop and reconsider using such high pressure. Does the rim maker have any recommendations on maximum tire pressures?
Have the rims had substantial use and possible thinning of the wall thickness due to brake wear?
Rim walls have been known to suddenly split due to high tire pressure, especially after considerable use with rim brakes has thinned the walls. Riding with wheels where you notice spreading of the rim walls is risking both failure of the rim and a possible crash.