If you don't mind me asking why are you going from a 3" back down to a 2.5"?
I have been kicking around putting a 3" on my 2013 163 but haven't decided if it is worth it.
I'm finding i ride more at home then in the deep. the 3 inch is just overall too much track for trail riding. it is mountain specific and i think the 2.5 would be a good compromise.
I bought a set of shears at Canadian tire years ago for cutting the lugs down.
They have a replaceable razor type blade on one side like a exacto blade knife.
I will take a pic of tool.
Works awesome.