Looks like you got a strong RTC! Moving him to another tank is a very good idea since the move should create some stress. Also, do put new water into the small tank as to further induce your cat to puke.

There are 2 ways to make a RTC regurgitate. One is as you mentioned, just feed till he overeats and he should regurgitate everything within the next 12 hrs. The other way is to feed and do an immediate water change. Regurgitation should take place within the next 2 hrs or less. Good luck :D

Do let ...