id say yah i have had my tsn for about 3 years and he is now 19"....i dont see him reaching 4 feet for another few years as they grow faster when they are young..
aslo ffeding them once a day will slow its growth..if you want it to grow fast feed it 3 times a day....if you get em small you will have 4-6 years to build another pond...and im sure you will if you are starting at that size
good luck with your fish