[COcyclist]

I have been toying with building one of these for my little pickup. For visibility straight out the back, you don't need a plexiglass as big as the back glass in the truck. In pickups the glass is closer to the back of the driver's head. You aren't even using the glass down by the driver's shoulders to see behind you out on the highway. There just needs to be a window a little larger than, and in line with the rearview mirror. I would suggest mounting the framework on the truck and take it out on the highway to see how small of vertical plexiglass you would actually need. A little scallop like Aerohead's should be fine. Some bicyclists use a little mirror the size of a postage stamp on their glasses and it works because it is close to the eye.