If you want to run the tubing through the wall of the tank and delete the nipple
then yes i think you need to run a thicker tubing such as the Du-Bro,kyosho or
fioroni. I have done that type mod to several tanks in the past and the thicker
tubing simply works better.

If you just want to double it up inside the tank on the nipple and clunk then no
you do not need other fuel line as the stock stuff works just fine for that. Both
my original tanks are done this way and I have not had any problems, just make
sure you run a piece of foam under the tank.