I was referring to the full scale P-51's fuel tank design location. Back when I was breaking a prop every 4 flights with the tank in the manufacturer's recommended location, up behind the firewall, and had tried all of the "expert's" fixes for nose over problems, I took a look at the full scale plane to see if there were any clues to a solution there. When I realized that all full scale P-51 aircraft always flew with the fuel behind the CG I decided to give that a try. The full scale plane's horizontal stabilizer-to-wing-area ratio is larger than most other comparable A/C so I thought that maybe the design engineers had done that to increase the horizontal stab's lifting ability. They had also made the elevator's leading edge thicker than the stab's trailing edge AND had contoured the elevator's leading edge to allow smooth hinge-line air flow at all elevator deflection angles. I am an old sailplane flier and had seen similar design features applied to glider control surfaces for competition gliders.
I researched P-51 test flight and design data but could not find any mention of airframe design referring to the tail group except for the high speed-low drag tip designs (which are different from the wing tip design). Axis warplane designers had studied captured P-51 airframes and had even flown them trying to discover the P-51's secrets but never attempted to copy what they saw. I knew that in order to successfully control a glider at rearward CG locations (for much better slow speed thermalling ability) changes in tail group shape and total effective area are required. And, I was already flying my competition gliders at a 45% CG location.
We modelers all know what happened to the P-51's flight stability when the extra rear tank was installed behind the pilot, but the Allied Generals decreed that the tail heavy condition that resulted was an acceptable risk compared to the additional long range benefit that was realised. Some units limited the amount of fuel allowed to be carried in the fuselage's rear tanks to lower the risk to pilots.
Since I was able to balance my P-51 models on the TF recommended CG and the rearward tank installation would never affect the CG, I started using it and never looked back. I no longer use glow motors so there is no need to place the tank near the carbureter. The only reason to place the tank near the firewall is to ease the glow carb's poor fuel-draw problem.
I can't say that I never have a nose-over but if it happens, it is because of a procedure mistake on my part, not a nose heavy plane. At one point I asked the APC prop manufacturer if there was a total time limitation on model props like all full scale propellers have. They replied that since most props are destroyed at low flight time in nose over accidents they didn't think a total time was needed. At that time several of the props I had been using had several hundred flights and a couple are still being used today. The smaller 20 inch size I had used when flying a 40cc gas engine are still good but I no longer use engines that small.