Richard, I have my fueler installed similar to "Roll On" with the Top Flight in-cowl muffler and it works great. As Paul said you can see the fuel through the front windscreen as it fills the tank. Also, if your pit area is somewhat quite, you can hear the fuel running into the muffler as it over fuels. It's kind of a gurgling sound. The effect is somewhat immediate. When you hear the sound - fuel will soon be pouring out through the muffler exhaust extension.

Mark Stafford