I was able to litteraly squeeze a Sullivan Flex 8 oz in my Uproar and I bought a 10 oz today thinking I could get it in the new Uproar, the problem with the Sullivan 10 oz (slant) is they are too wide in the front but actually shorter than the 8oz!! if it were 1/4 in narrower at front, it would go in!!! I am giving serious thought to heating up the tank and forming it to fit, I have done this before and it works pretty well. I prefer the slant types as I just run the fuel lines up through the hatch rather than make a big hole in the firewall. I tilted my GMS .47 about 20 degrees to the left to put the engine weight more centered and the added benefit is the exhaust almost goes straight up and the airplane doesnt get too messy. I get a good 12-15 min flight with the 8 OZ tank but would like a bit more.