This is the latest break in proceedure recommended by Arrow-Racing. I had already broken in both of mine before they emailed me this so I have not tried it yet but will on my next engine or rebuild.

Upside Down Engine Break in:
If you already own a break-in bench, during break-in please turn the whole bench with the engine upside-down to assist with extra lubrication at the "Top-Dead-End". After the end of each tank (125.cc) of running on the bench, turn the flywheel to the "Bottom-Dead-End" position to allow the piston to cool at the most bottom position of the sleeve. Start the break-in process again only after the temperature has dropped to less than 45˚ Celsius. Continue with this break-in process for at least 1 to 1.5 liter (3/4 of a gallon) of 25% - 30% Nitro fuel before actual running on the vehicle. We use about 2 liters of 30% Nitro fuel for running-in on the bench with the engine running UPSIDE DOWN!
When the engine is on its first run on the vehicle, it is a common sense to richen the fuel on both the low-speed needle and high-speed needle with slightly higher idle speed! Your vehicle should sound like a 4-stroke engine. However, at the same time, you should also check the temperature and try to keep it up at between 80˚ and 90˚ Celsius to maintain a good break-in temperature to ensure proper expansion of the sleeve.
After 5 to 6 (125c.c) tanks of fuel running on the vehicle, remove the glow plug and check the compression by turning flywheel. If the flywheel stops turning before the piston reaching the TOP-DEAD-END, this means that the piston/sleeve is NOT YET broken-in. This also means that you SHOULD NOT run your engine at FULL THROTTLE for a prolonged period of time (we're talking about 2 to 3 seconds only)!!! Continue with the break-in process until you find maximum compression while turning the flywheel with a slight bite between the piston & sleeve. This usually takes another 3/4 of a gallon.

So Arrow recommends 1.5 gallons of fuel to break in. When done this way, the rod, piston & sleeve will last 8+ gallons of fuel. Since the GTR has a very strong pinch, racing the engine before the 1.5 gallon mark will put more stress on the rod and piston/sleeve so the life will be reduced. The mechanical pinch should be gone when an engine is fully broken in. To check it, remove the plug while the egnien is warm and turn the flywheel over. If it gets stuck at TDC, then it still needs more break in.