Started as a 5-3-1-1 cube as per https://www.reddit.com/r/mtgcube/comments/7ig6yn/i_want_to_make_my_first_cube_as_an_unstable_cube/

Main tweaks are additional cards from other un sets and a small number of black border cards to support set themes and improve fixing.

Here are the notes from the reddit thread above on creating packs:

I am not treating rares and mythic rares differently in terms of rarity. EDIT: actually I think I will, the change is simple, just remove 5 non-contraption mythic rares, 3 contraption mythic rares, and 2 contraption rares from the pool at random (without looking) each time you want to setup a draft.

For the common "variant" cards I'm doing 2 of each A version and 1 B, C, and D (for "secret base" I'm doing all 5).

I will include 1 of each "uncommon" variant card and 1 of each "rare" variant card (if the price of Very Cryptic Command drops).

Here is how I plan on creating packs (I do not try to avoid double commons in the same pack, etc.).

Separate cards by rarity and by contraption/non-contraption (treating rare and mythic rare the same). This gives three piles of cards. Contraptions should be sleeved in clear sleeves or in a different color of sleeve.

Shuffle all 18 uncommon variants (Knight of the Kitchen Sink, Sly Spy, and Garbage Elemental) and randomly pick 9 of the 18. Include them in the non-contraption uncommon pool.

Shuffle all 18 rare variants (Very Cryptic Command, Ineffable Blessing and Everythingamajig) and randomly pick 3 of the 18. Include them in the non-contraption rare/mythic rare pool.

Deal 24 (or 3x the number of players; or 6x the number of players for draft) "non-contraption packs" of 8 commons, 3 uncommons, and 1 rare.

Deal at least 4 (or at least half the number of players; or equal to the number of players for sealed), but preferably 1-2 extra "contraption packs" of 8 commons, 3 uncommons, and 1 rare.

Shuffle all the contraption packs together, so that the rarities are all mixed, but with the ratios mentioned above (alternatively the step above can be skipped and one can just shuffle a mixed pile of contraptions in an 8:3:1 ratio).

Deal 2 contraptions from the mixed pile to each of the non-contraption packs, so each pack has 12 non-contraptions and 2 contraptions (in different color sleeves) for a total of 14 cards a pack.

If you care about mythic rares being more rare than other rares, randomly remove half of them from the pool at the start.