I think we should use low level notes at all levels of crafting. At high levels of crafting, all notes should be used.
low level ships require low grade
mid level ships require mid grade and low grade
high level ships require high grade mid grade and low grade
for example,
upgrade could use 1 high note, 2 mid notes, and 3 low notes.
a santisima could use 4 high notes, 3 mid notes, and 2 low notes.
I think it would be a great way to give new players a meaningful way to earn money and contribute to the economy in a meaningful way. This could help a lot of people get over the initial economic hump, help them break into crafting, and encourage player retention.