Can't wait to resolve some Explorations and Manabonds again unmolested by MMS.
As for:
I would say the maindeck flex slots are:
1
Tranquil Thicket4
Mishra's Factory1
Urborg, Tomb of Yagmoth
I would personally try to squeeze Karakas into the maindeck just to free up one slot in the SB. How necessary have you found Urborg in getting maze/tabernacle/chasm mana for the Mindslaver lock? Does it serve any other function really? That would be the first card I would try taking out for Karakas.
I like Mishra's Factory, as it gives us more ways to attack Jace and block an early Goblin Lackey, but some seasoned pilots argue that the singleton Creeping Tar Pit is enough manlands.
Any reason for not running at least one
Ghost Quarter?
As for the sideboard, I would love to hear your explanation for your choices. My biggest concern is that there currently aren't any card advantage alternatives to the Loam engine (ie.,
Dark Confidant or
Crucible of Worlds). That seems risky if facing any hate, esp.
Extirpate and
Surgical Extraction, which will probably show up fairly often.