If you use the bear trap strategy which is if you lead it into a Dino gateway that is shaped in a triangle and with a bear trap in the middle (Large Beartrap) and when it is stuck you must put a dinogate behind it to trap it and then knock out. (hope this helped and "If" I win could it be an Xbox voucher, thanks.)
When breeding two max level rexes to have a super baby, DON'T EAT THE EGG!!!! I've done this twice on accident(meaning to drop it) and each time it takes me a couple seconds to register wtf I just did and then I have to wait to mate again. Sad day. Weekend ruined. Great way to start off the new year! Lol
Rex baby consumes meat at about 1 meat per 50 seconds. Each meat gives about 50 food, with a food drain of 1 food point per second. So.. 1 meat = 50 seconds of feed. 1 stack of meat is 1000 seconds/16 min. A stack of meat takes 12hrs to full spoil. So.. on 1x, at 6% maturity, a baby rex can be left to fend its own till juvi... this is even with a 2 hr safeguard to be very safe. Honestly... 5% would work also. Hope these statistics help!
If you bring your high health Spino, hit the Rex once and it will just get distracted attacking your Spino instead of you. Just dismount and tranq it then when its running away just chase it as you tranq it then it shall get unconscious. My plan became successful. The rex i tamed was a.lvl 10.