I disagree. With our lap belts on and pulled down tight, we have zero issue with the laps riding up due to the shoulders pulling them up. We have been in a rollover and didn't have any issues with the belts coming loose or riding up. We were actually very comfortable once the truck stopped rolling and we were suspended upside down. Most if not all 4 point belts such as the OP has don't even offer sub belts. Those belts can't even have the shoulders removed from the lap belts. I am not saying the subs are useless but in most of my low speed situations they shouldn't be needed. Should we wear them to keep us from sliding out of the bottom of the belts incase of a long continuous end over end, probably.