I suggest you to check the stress analysis for the required load cases. After the analysis and acceptable stresses/displacement/support loads/nozzle loads extract the hanger loads.
Spring hangers/constant load hangers should be selected as given by the analysis (there are exceptions for this. In case the pipe diameter is small and auxiliary equipment weight of the support on the pipe is high, vendors can make the necessary changes in case these are not considered in the model). Do not introduce additional percentage on the loads of spring and constant load hangers. However you can make the load increase on the other type supports (such as clamp bases, lift off restraints, hanger rods, guides etc...) not on the spring/constant load hangers.
If you purchased the spring hangers, make separate stress calculations with the purchased hangers, and see the results before implementing. If the results shows you it is going to cause problem on the piping, do not use these hangers. Sometimes playing with hanger locations may provide the required correction to accept the hangers, but it is too difficult task and may give you other problems that I do not take into consideration at the moment.