i did say you have to modify them. and the intercepter vest was not bulky at all. thats why the Marines loved it so much because they were small and light weight. they did leave the arms vulnerable though.
Add some level IV plates and you'll be good to go if someone decides to drive-by you with an AP 30-06 round too!!!
Seriously though, wearing an actual (as in bullet proof) armor carrier on a motorcycle is kinda retarded IMO.