MY buddy has a 18 inch rtc with a 14 inch gar in the begging it tried to go after it but gave up... But the size difference between your rtc and gar s deadly
your either a huge troll or you don't have a clue about fish care and basic knowledge of them. your gar will soon eat your red tail at that size. also the idea your gar will only get to 4 ft and your red tail to 2ft is an absolute joke. your red tail will get to 4ft and your gar 6ft+ if your give them the proper care they require and deserve, if you can't do that i suggest you take them back to your lfs asap.