If youre designing for printing: start from 2.5 3.5 inches as the trim size, then add bleed (more on that below)
While the card not doing anything when you cast it is a shame, you only need one turn with this thing to completely transform your board state
It also has Trample, meaning if your opponent blocks with a creature and that creature is destroyed, if Bloated Contaminator has more damage available, that damage will go through to the opponents life points
For two mana, you can force your opponent to put an attacking Creature on the top or bottom of their library
If you are building for the game against a mill deck, you've sacrificed the efficiency of your deck against every other match
And that win condition is a good one