The best way for me to knock these guys out is to place down stone pillars in a line but spaced out to where you can easily squeeze through but too small for the rhino. Then lure it to the pillars and run between them. The rhino will get stuck on it and if you're lucky, it'll be aggro'ed on the pillars and not you. From there you can start tranqing it and if it goes around the pillar line just go through the gaps and continue tranqing. Dont get too close though cause they can still hit you through the pillars. Keep tranqing until its knocked out or runs away from low torpor. If it gets unstuck from the pillars and runs away, chase it and keep tranqing if it turns around to try and kill you just lure it back to the pillars. This method does require timing, positioning, and being cautious.
Use an argy trap! I was able to tame 2 lvl 150s with one. 4 stone gateways placed in a row with gates at either end once you have got the rhino in. Make sure you have a beast to protect it in case of things like rexes and sabers while its knocked out. They're so easy to tame and are absolutely brilliant once tamed.
Ez tame even for early game , just use 4 billboards, put around rhino when still unaggro and then when the rhino is trapped with the billaboards just start shooting tranqs . ( Can use wooden billaboards)