Welcome. I think you'll be less safe with four points than 3 points on the street,but If you are going to be running 4 points,make sure that are legitimate 4 points,not a 5 point run without a crotch strap. The crotch strap keeps the lap belt from being pulled upwards and into your organs when the shoulder belts get tugged hard in a crash. Scroth makes legitimate four points,that have give in the shoulder belts to prevent this. The less rigid straps also lessin your risk of a basilar skull fracture,which will kill you.Also before you decide to run harnesses on the street tie your self into your seat,not able to lean forward to see around things,change the heater controls,or work the radio and drive around a bit,you probably won't like it and decide to save your money. I've run harnesses in some of my toys and wouldn’t want them on the street. Good luck with your project.