My 1980 Silverado has a cab height steel cap.
Rear vision on all of my vehicles is good/great with the convex side mirror stick ons
Just learn to know where our rear wheels are in reference to the rear corners &
side of the vehicle
The steel cap has three locks. Center (OEM) and on each end of the rear hatch
door. I put them in one Saturday
You can only slow down the bad guys and keep out the good guys...
Fiberglass cap would weigh less than my steel cap, but can take it off and put
it back on myself (mid 60's, weigh approx 180). That cap weighs in around 200 lbs
give or take (never weighed it)
Nephew has a nylon canvas cap that folds out of the way and won't last
as long as my steel cap, which is over 30 years old