I'm having a hard time understanding something related to the fire in the debris pile.
Both towers were 110 stories high. According to the Popular Mechanics website, WTC 1 was struck between the 94th and 98th floor and WTC 2 was struck between the 77th and 85th floor. The fire spread upward and down-ward until the collapse after 102 and 56 minutes respectively.
Popular Mechanics states:
... NIST also believes that a great deal of the spray-on fireproofing insulation was likely knocked off the steel beams that were in the path of the crashing jets, leaving the metal more vulnerable to the heat.
Given a "pancake" collapse of both towers, why is the material at the bottom the hottest? Wouldn't both buildings have approximately 70 or 90 floors worth of material including strata of intact fireproofing and insulation laying in a pile with only approximately 60 (40 + 20) floors of burning material on top?
The Popular Mechanics web site also states:
The NIST investigation revealed that plane debris sliced through the utility shafts at the North Tower's core, creating a conduit for burning jet fuel--and fiery destruction throughout the building. "It's very hard to document where the fuel went," says Forman Williams, a NIST adviser and a combustion expert, "but if it's atomized and combustible and gets to an ignition source, it'll go off."
Burning fuel traveling down the elevator shafts would have disrupted the elevator systems and caused extensive damage to the lobbies. NIST heard first-person testimony that "some elevators slammed right down" to the ground floor. "The doors cracked open on the lobby floor and flames came out and people died," says James Quintiere, an engineering professor at the University of Maryland and a NIST adviser. A similar observation was made in the French documentary "9/11," by Jules and Gedeon Naudet. As Jules Naudet entered the North Tower lobby, minutes after the first aircraft struck, he saw victims on fire, a scene he found too horrific to film.
This would seem to explain how fire reached the lower floors or even the basement but two things strike me as odd.
I thought I read somewhere that the WTC was designed with a compartmentalized elevator system to prevent fuel from travelling the length of the building due to the 1945 B-25 accident at the Empire State building?
Secondly, if a substantial amount of jet fuel travelled down the elevator shafts causing fires in (let's assume) the basement, does that leave enough jet fuel at the impact point to weaken the steel?
Again, from Popular Mechanics:
But jet fuel wasn't the only thing burning, notes Forman Williams, a professor of engineering at the University of California, San Diego, and one of seven structural engineers and fire experts that PM consulted. He says that while the jet fuel was the catalyst for the WTC fires, the resulting inferno was intensified by the combustible material inside the buildings, including rugs, curtains, furniture and paper. NIST reports that pockets of fire hit 1832°F.
Even as a "catalyst" I'm having a hard time with this.
Lastly, the impact of the second plane into WTC 2 resulted in a massive fireball which I believe is attributed to jet fuel exploding outside of the building. In this instance does the jet fuel explode outside, act as a catalyst and travel down the elevator shafts to feed fires in the basement?
Please note: I'm not trying to stir up trouble but rather just looking to understand what, in my mind, seems like a contradiction.
** Edited for formatting issues
I tend to get a bit short-tempered, as well, on a regular cycle while dealing with some of these people 
