Fuel Consumption

My engine is purchased with the kit around 2000. First flight was 2021 and it has now flown 150 hours in total.
Mainly the last 3 years. - No previous owners.
I had rough engine around 50 tacho hours ago.Tried everything to make it run smooth. Renewed everything in the carburetors installed new ignition, new plugs.
I finally found out that  had a minor leak between the carburetor and the rubber ferrule.
So..I'm sure that the carburetors are fine.
I will go on a 2 hours straight flight.within a couple of days and double check the consumption.
My plan is as follows:
Top up the tank until it is 'spitting' out the vent.
Start the engine -warm up - take off with 5500 rpm - climb to 2000 ft above the airfield - go into the circuit and land - position the plane on same spot where it was refueled - top up with fuel until the spitting point - record amount of fuel.
Next step (next day) Do the same exercise, but when reached the 2000 feet, I will continue flying in 2000 ft with a fixed setting for the next 2-3 hours. Return to the same spot above the airfield and land as before.
Refuel to the same point and deduct what I used for the earlier up and down test. Then I will find how much fuel I use for the straight flying time.
Well, time will show.