Is your feature request related to a problem? Please describe.
this modpacks seems to assume copper and silver are added in mods. therefore the copper and silver backpacks are redundant. A good decision, imho... at the time

Describe the solution you'd like
but now copper is in the minecraft base game (vanilla), I think it should be it's own category. that would give some use to the copper.
And for the recipe for the iron backpack, not the normal, but the copper backpack should be used. (and the iron should be bigger then the copper one, by default.)
So something like: Normal [3 rows] > Copper [4] > Iron [5] > Gold (or Silver) [6] > Diamond [7] > Obsidian [8]