Clicked into the first one and got a thing about the insulation between the tanks - the 3rd video in the playlist was about them hiring surfboard makers to do the honeycomb insulation between the fuel tanks, since they had more experience working with the materials in the heat conditions.

Just another kind of "the space program was amazing" thing - the sheer diversity of people who got hired on to contribute is continually surprising. An amazing tribute to the pragmatism of NASA under the conditions.