I use G clamps on all my lighting, and recently, safety wires on selected items.
As I use the Ultimax stands, which utilise square tube for all their poles/gantry pieces, then the clamps which I get from them are square also, which gives things a pretty snug fit.
The safety wires are all long ones, with a spring loaded clip at one end, and a closed eye at the other end. I'm able to wrap the wire around the bar and under the lighting bracket (not just the g clamp) 3 or 4 times, before latching the clip to the closed eye.
Its worth remembering that there are different types of safety wire. Some are strong enough to hang roadies from,

while others were only designed to hold accessories from eg: Par can barn doors, filter gel frames, large lens caps etc. So check load/capacities before ordering any.
I once saw a disco using safety wires instead of G-clamps. Really, no G-clamps at all, just safety wires holding NJD Datamoons and Twisters onto an tripod with 2 t-bars across it.
Funnily enough my PLI doesnt have anything specific in the small print about me
needing to use any type of secondary safety precaution, but I like to use em.