not needed unless you want to be legit. I'm running 8.5" and stock slip. you will still need to drop tcase a bit and ensure proper length of driveshaft to ensure full engagement during frame flexing. longer wheelbased rigs, like trucks, have better driveshaft angles to work with wheres wranglers and xj with shorter wheelbase need compact driveshafts and better rotational angles during flexing. with that your upgrade mainshaft added strength and will a little gumption most can handle install. also with this type of setup you could have one spare driveshaft for front or rear . and typically if your considering installing one you most likely have tcase that is due for maintenence and this be ideal time for such repairs or upgrades to thicker chain and bigger planetary gears. oh so many options right, do you need sye..? no. but if have the cash to get it then why not. 🤑