I'm looking to get butler creek flip up covers for my new viper 6.5-20x44 and was wondering what size to get. According to Vortex the eye piece is 1.5" and the objective is 2". Should i buy the caps that are slightly smaller or the ones that are slightly bigger. They don't list ones for those exact sizes, i'm thinking the ones that are smaller but not sure if they have any flex to them.