Thanks Brett. I've connect with Kaz. For what it's worth I have a couple of the Windy Urtnowski 7 oz carbon fiber tanks and they weigh less that 1 oz. I have one in my Shark 45 that has well over 600 flights on it with no issues with the tank. The pilot yes, but not the tank.
I remember seeing some very fine patterns with that Shark and the PA61 that was in it! Fine flying airplane, and good running engine.
Is it still flying?