The first time I filled the tank on my 7, after building it from 2 wrecks, the fuel gauge read only 3/4 when the tank was filled up the filler neck. When checked I found the float had something like 15 to 20% of its capacity full of petrol.
Knowing that wood swells when wet with water, I drilled a small hole in the float to get the fuel out, then plugged the hole with a wooden plug carved from a Kebab stick, & tapped ti gently into the hole, trimming it almost flush, hoping that wood swelled in petrol in the way it did with water. The gauge still didn't read totally full, but is only half the needle width below full.
That was about1993, & the float was still empty when last inspected about 3 years ago, & the gauge still reads the same 27 years later. I think wood must swell in petrol.