The writer, whoever he/she is, seems to have missed the fact that the P51, in it's B/C form, didn't have the fuselage tank from the start, but had, as did all versions of the Mustang, wing tanks as the main fuel supply. The fuselage tank, useable capacity I believe 85 gals, was added as a requirement for extra range, along with drop tanks, in the ETO.
The P-51B-1 arrived in ETO without the fuselage tank. The first production models carrying the 85 gallon tank was the P-51B-5 and C-1. Kits were provided to re-install in earlier versions of the -5 and -1 shipped. Also changed was the replacement of the 1650-3 engine with the 1650-7. Slightly less high altitude but better low to mid altitude performance.
The 85 gallon tank when full not only created the aft cg issue but one of the problems was the 'porpoising' effect which wasn't fully solved until the metal elevators and kits were introduced in the P-51D-10 - and ultimately solved with P-51H's 14inch fuselage extension
I couldn't finish reading the article, as there were so many mistakes, inaccuracies, and downright b*ll*cks, that I gave up!
For instance, when did the Spit IX get a Griffon engine? And, without going back to the pic posted to check, I think it was a Spit 24 anyway!!