Problem: drums aren't big enough for my needs and capacity can't be meaningfully upgraded like chests or barrels

Solution 1: higher capacity drums with a larger stack size and/or max # of stacks made from rarer materials (this seems the worst option and inconsistent with your approach)

Solution 2: unique upgrade(s) for the drum

• stack size upgrade increases stack size by a multiple of x (1.5 or 2 seems best) to a reasonable maximum such as 8096 (the recommended RAM usage for heavily modded games, as an Easter egg)
• max # of stacks upgrade, adding 5-10 each to a reasonable maximum such as 288 stacks (the same max storage as a fully upgraded chest/barrel)

Alternatives: I could learn some rudimentary item sorting redstone and just use the compact chests/barrels instead. Less convenient, but serviceable.

Additional context: other storage mods seem to have high-capacity storage similar to drums with larger stack sizes and max # of stacks, but are generally absurd (storing millions of items). I prefer the more reasonable numbers your mod allows and how it stays mostly true to a vanilla feel. Only using the max stack # idea might be best to preserve that, since higher stack sizes isn't a vanilla feature. Also, it feels weird to sacrifice 224 potential stacks of storage for the convenience of drums and upgradeable drum storage makes the mod feel a little more consistent.