Julian,
The new tank parts furnished with the kits no longer have the sight glass since Van's incorporated a mechanical gauge on top of the tank. Of course, you have eluded to the main issue and that is you no longer can actually see the fuel level in the tank. The sight glass would indicate fuel level right up to "full", and the mechanical gauge stops a couple of gallons short of full so you always have to be careful topping up the tank.
There is always the question whether any gauge is working, however the needle on the mechanical gauge will jiggle when you move the airplane slightly which is a pretty good indication that the gauge is not stuck. Cross checking with the electric sensor indication on the EMS confirms the mechanical gauge.
As the only pilot of my airplane, I always am aware of fuel level and I don't use a dip stick. If others were flying the airplane I would be more inclined to use a dipstick to double check the level before flying.
I don't try to lift fuel containers up to the filler neck. Instead use a hand cranked transfer pump with a ground cable.
I recently let the transfer hose slip out of the filler and splash the rear window. Very careless of me and I am currently replacing the window. I did not have the window sealed as per the latest plans and it instantly was crazed and cracked. Be careful refueling!
The picture also shows the right angle fitting I now have in the hose to prevent it from slipping out of the filler. Should have done that a long time ago, along with sealing the window, and probably would have saved myself a couple hundred bucks.
Marty, sorry for the thread drift...