When filling an underseat tank, like the one in my '21 Touring, what do you do with the seat, and what do you prop up the "lid" with? Where do you carry your gauge (dipstick)?
I pull the seat bottom out. Usually lay it over the top of the seat. The lid over the tank has a hole in it so I don't have to lift it up.
I slide the front seat cushion off and onto the floor. _You can prop the lid open with a piece of wood. _The dipstick can go pretty much anywhere. _
The important thing about refueling a Model T is to avoid spilling gasoline on the outside of the tank where it would quickly flow around the tank to the bottom, from which it might then drool onto the hot exhaust pipe. _If the gasoline drippings catch fire, the flame could follow the trail of gasoline back up and over the tank and into the opening at the top. _Make sure all the gasoline goes into the tank. _
Also, don't fill up to the tippy-top. _Leave about a gallon's worth of slosh space so the gasoline will have a little room for expansion if the day's temperature rises.
I just turn the seat cushion on its side. There is no lid. I made a box that sits behind the gas tank, and the stick rides in there.
I stand my seat up against the windshield on the floor or sometimes I lay it on the hood. My board over the tank is loose so it just props up against the seat back.
Neither of mine have the "Lid", so I just take the right hand end of the seat cushion and rotate it forward laying in on the floor, leaving the left end still up on the seat riser.
I take the seat base out and rest it in the pickup bed when I'm adding gas. Sure gets some funny looks at the gas station!
And the "technology" didn't change much in the next 20 years. My WWII jeep has the drivers seat cushion lifting back and the gas cap is acessable through a hole cut in the fixed seat pan, the cap is on a chain so it doesn't get lost (good idea for T owners) and you manipulate the jerry can or fuel line between the steering wheel and the upraised seat cushion.
I'm building my WWI vehicle with a wooden body and bench seat. I've fixed the drivers seat bottom, but hinged the passenger for fuel fill up. I also built a fairly large storage box by the tank for fuel sticks, registration paperwork, current license plate, etc. Only the passenger has to get out for filling up.
My Dad's '36 Dodge Truck had the gas filler on the driver's side, just in front of the seat. When we sadly sold the truck (long story there, not relevant) the new owner had the same problem I was having; the truck would start just fine, but then quit running. Turned out a bit of seat cotton had fallen in the tank and would float around, until gas started flowing to the carb, and it would be sucked onto the line opening, stopping flow. Then it would float away again after the engine quit.