When solving a puzzle with triple-stacks at the top and bottom, it helps a lot when the first two Across answers are gimmes. Among my earliest memories is that of my father reading "Treasure Island" to me and my sister. The tapping of Blind Pew's cane, and Long John Silver's line SHIVERMETIMBERS are as indelible as the "black spot." And HOTELCALIFORNIA, well, anyone "of a certain age" will know that lyric, I imagine.
After that, the somewhat ad hoc ETHNICRELATIONS (Ways in which different cultures interact) is symmetrical with HATERSGONNAHATE ("Don't sweat the naysayers"). That's an interesting juxtaposition.
I liked the straightforwardness of "It travels at Mach 1" for SOUNDWAVE, and FUNSIZE (Smaller than usual, endearingly) brought a smile. Seems like a lot of old presidential trivia today - ELEANOR (Longest-serving U.S. first lady, informally), JQA (Presidential monogram of the early 1800s), and WHIG (Daniel Webster or Henry Clay). And it almost seems like the Non-QMC "Water colors" (AQUAS) is a DADJOKE.
As usual with a stack puzzle, there is some straining in the support structure: ENORM, HOTTO, IFA, RATON... but nothing too too terrible.
I got lucky knowing a few things and it really made this one go by quickly. 7:42 on a Friday still seems very fast to me.