Actually, what Earl is describing is a mix of Mustang stories, some of which were never true. Even the 'H' model had the wing LE fillet removed, not enlarged. Likewise, the landing gear was lighter, not heavier, as this was part of the Mustang total redesign. The 'H' was the fastest propeller aircraft of WWII, but it did not see action. The whole purpose of the redesign was to produce an aircraft that would be faster to maintain, and repair, but it was no better at ground attack than the earlier versions (except the A36 type, which was superior).
Next I expect to hear how the F-82 is two Mustangs bolted together, which is also untrue.