Since I'm waiting for a large shipment of parts from A/C Spruce to continue with the brakes and controls, I dove into the fuel system. I had a good look at the fuel tank. It's a very complex assembly with a lot of welding to it. It's a single unit but there are 2 separate tanks. The upper tank feeds the lower and the lower tank feeds the engine. There is a fuel pickup at the bottom of the lower tank. For aerobatics, the fuel pickup is a flop tube in the lower tank. This is a common arrangement on aerobatic aircraft that can fly inverted. This allows the engine to draw fuel regardless of orientation of the airplane. At least, until the lower tank is consumed. If there's still fuel in the upper tank, the fuel will drain into the lower tank when the plane is upright again. Most planes that have this arrangement have two separate tanks with external plumbing to connect the two. In typical Dalotel style, this was done a more complex way. The tanks are built as one unit and connected internally. There's a lot of complex welding with tubing and stiffeners/baffles welded in the tank. All beautifully done but much more expensive and complex than it needs to be.

I also had a good look at the fuel selector valve. Applying some lung pressure to the ports I was able to determine that it's a three way valve with an upper port, a lower port, and a common port out the side. Interestingly, this selector valve doesn't use a ball valve to select between the ports. Instead it uses a piston system. The valve pushes a piston to close the respective inlet. When the valve is in the middle position, the pistons on either inlet are closed. That's right. The valve has a port open at one extreme, all ports are closed in the middle position, and then the other port is open again at the other extreme. Learning this, it's not surprising that the engine was accidentally shut off in flight when the pilot was switching the fuel selector. Why would you go from an operational position, to a closed position, to another operational position. It doesn't make sense to me. For that matter, there's no reason whatsoever to draw fuel from anything other than the flop tube pickup. I think I'll simplify the fuel selector system when it comes down to it.

Tested the fuel level with the indicator on the panel. The system still works. See attached pics.

Riveted to the upper cowl surface of the fuel tank, so that it is visible inside the airplane is a placard. See attached pic. With a non-French keyboard, the wording is this:
Cet aeronef voie sous le regime du certificat de navigabilite restreitn. Il ne repond pas necessairement aux conditions de delivrance du certificate de navigabilite normal. Son utilisation dans unbut lucratif est interdite. Arrete du 23-10-62
Roughly translated, it means:
This aircraft operates under the restricted certificate of airworthiness. It does not necessarily meet the conditions for issuance of the certificate of normal airworthiness. Its use for profit is prohibited. Judgment of 23-10-62

This is not much different than the placard that we're required to display in amateur built aircraft in Canada. The following is required and will be displayed in this plane once completed since it is being restored/rebuilt as an amateur built aircraft.

YOU FLY IN THIS AIRCRAFT AT YOUR OWN RISK.
THIS AIRCRAFT DOES NOT COMPLY WITH INTERNATIONALLY
RECOGNIZED STANDARDS.

VOUS VOLEZ A BORD DE CET AERONEF A VOS PROPRES RISQUES.
CET AERONEF N'EST PAS CONFORME AUX
NORMES RECONNUES A L'ECHELLE INTERNATIONALE.