I'm pretty sure your North Viper 75% mast was not quite right for the sails you have,
Do you have any idea which model Viper mast (when it was made) you broke.
I do not know much about GUN masts, bit I do know that if you go from a 75% carbon mast
to a 35% carbon mast, you will definitely feel the difference in weight and it will not be a good feeling.
I would be looking for an Ezzy/Gaastra/ Powerex/Sailworks =>75% carbon 460 cm IMCS 25 mast for your sails.
As unreg suggests, if you spend a little extra cash on getting the recommended mast from the loft that made your sails, you will get the full performance from both the mast and the sail.