I'm confused why you can't do both for #5? It seems safer to use both

Well you are "risking" it if your carseat manual states the handle must be up. Which is why it's SO important for everyone to read their manual.

Either way I wouldn't risk it :)

Brittany....that's only true of some seats. Many seats it doesn't matter if the handle is up or down. Some specify that the handle should be up. Some down and some it doesn't matter.

Unless you have a Combi carseat and NEW Ford Edge you CANNOT use both. Period.

One that my hospital gave me when we were discharged is when the car seat is in the car the handle should be clicked down and not above their head. In case of an accident it can detach and hurt them very bad.

Only 1 brand allows for it and only 1 brand and model of car allows you to do it. Which is why we say "never" because the likelyhood of someone having the 1 type of seat that allows it and the 1 car that allows it are slim to none.