What I use to keep my mirrors from moving is steel fishing leader. It is sort of hard to explain but there is a small bracket that sticks out from the hood seam which I attach one end of the leader to. The other end of this leader is attached to the support arm of the extended mirror. Those that are interested I can email me for some pics. At speeds of 50mph on up these things don't move. Even wind gust from other vehicles whether I being passed or in the passing mode myself don't phase 'em...
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1997 3500 SLT, Ext cab, 5spd, TST #11, GV Aux Trans, BD exhaust, Kelderman Air Ride, 60 Gallon fuel tank, Clifford Security, Reese 20k 4way 5th wheel hitch, Boost/EGT gauges, K&N air filter, Rancho RS9000 shocks, Brush Guard, DZee full length running boards.