I posted this in the video comments but there's less noise here:
You should try an SD card rated for "A1" - there aren't many yet, and I haven't seen any "A2" ones yet, but they are supposed to be much better for random access and running applications (hence the "A") from.
I actually have two systems at home running on flash cards - one 90s 486 laptop running off a bog standard SD card (not A1, but is probably still faster than its original disk) and one custom linux router booting from a CF card.