Hi, I use two tanks on my MTA4, the main 150cc and a secondary 75cc connected in series.
Easy to connect up, remove the fuel line going to the exhaust from the main tank and run it to the main fuel out on the second tank. Then take the pressure line from tank to and connect back to exhaust. The second tank will run down first the go to the main tank. I get no leaning problems and a 20min run time. Have a look at the MGT forums for more details http://www.monster****rum.com/