Who ever did the engineering for DSI put those values in there for a reason. It's generally not a good idea to over ride the SME.
As said before, I advise identifying the responsible EOR, and make them put their requirments in writing if they have not already done so.
http://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse is what happens when they get lazy, greedy, or are just stupid.
PT cables are not something to be tinkering with loosely, should it fail due to this engineers change in calcs, and you don't have
those requirements in writing, and or he is not the responsible EOR, take a guess who is going to be blamed should some people get killed in a collapse.
Regards,
Gerald