My Cube has been sitting at 720 cards since the beginning - I like playing with as much cool cards from Magic history as possible as well as having variety from draft to draft. Nevertheless, I decided to trim it down a bit to get some extra consistency and a little more power during gameplay.
What felt challenging was to cut cards while trying to keep the Cube balanced (in geral) while also maintaining support to the existing archetypes (the usual Cube archetypes are supported, but with an extra push to Green Mega Ramp, artifact.dec, Twin, and Tokens - mostly based in white but with support in all 5 colors) and trying to keep some pet cards. I also tried my best to keep the overall CMC under 3 and luckily I was able to do it.
What felt challenging was to cut cards while trying to keep the Cube balanced (in geral) while also maintaining support to the existing archetypes (the usual Cube archetypes are supported, but with an extra push to Green Mega Ramp, artifact.dec, Twin, and Tokens - mostly based in white but with support in all 5 colors) and trying to keep some pet cards. I also tried my best to keep the overall CMC under 3 and luckily I was able to do it.
Anyway, here's the full breakdown, for posterity.
Former DCI L2 Judge
My old Cube podcast on ManaDeprived, with Goodking and artbcnco: http://manadeprived.com/podcasts/mtgin3d/
You can find me on Twitter as well.