I had two of the IMS 4.7 Gallon Tanks and both leaked from the Fuel bungs in the wings
IMS was very helpful and easy to deal with but in the end I decided to go with a Safari 3.7 Gallon Tank.
Still not satisfied with the range, I searched the Internet and discovered Camel Adventure Tanks
The tank is very well designed and works great. It is slim and light and holds an extra 6 Liters or 1.6 Gallons of fuel that feeds into the main tank through the vacuum line. The Aux tank always empties first and so you don't even notice the weight at all.
Just something to add to the Leaking IMS tank posts. Once the Bungs start leaking i do not believe they can be fixed anymore. My leak occurred not between the brass threads but between the bung and the plastic.