Playtesting is a crucial part of refining your deck
The Commander Game Changers list, as well as the Bracket system, is a soft indicator of the cards that could be added to the ban list
If the whitening is on the top/bottom/corners then it cannot be hidden by the slab and will get pushed down to a 9
Paying 6 mana over two turns to turn The Ur-Dragon indestructible seems okay, but the deck doesn't have much room for colorless lands, so I don't think I'd want to include something of that nature in the deck unless you really want your creatures to be indestructable
Although the size distinction between Jumbo XL and Jumbo L is delicate, it is considerable when choosing protective accessories
The most common choices are either spells that affect two different permanent types or ones that hit a permanent type, most usually a creature, and a player