I have experience with Uba Stax so I can speak from the other side of the aisle.
Because Meandeck Gifts does not main deck Welder Removal, going for the Tinker->DSC win is much tougher. Sure you can cast Will empty your graveyard of artifacts and then Tinker RFGing your sacked artifact but it is generally pretty tough. Playing against Uba Stax you want to go for the Tendrils win.
Actually, I would say you are 100% wrong here. While they don't have welder removal, like you stated, most decks playing against UbaStax would win MUCH more if they went for the fastest Tinker humanly possible (for Trike or Colossus) meaning use any tutor you can to find tinker and cast it turn 2/3. Save your force/drain for the welder. Thats it. Tinker is my worst enemy, and anyone who plays first turn blue mana/mox and mysticals for recall instead of tinker is my best friend. And I apparently have a lot of best friends.
It should be fairly difficult to go for the Tendrils kill with all the lock pieces bearing down on you unless you can get off a few quick massive artifact bounce/destruction spells. I would always go for the Colossus kill against UbaStax.
Mystical Tutoring for a second Turn Tinker is a usually a strong move on the play. On the draw it gets worse. That said I still fear Rebuild. Even with a ramped Smokestack, Tanglewire and Uba Mask if they have a third Island out during their upkeep they can bounce everything, replay all their moxes, Drop an Underground Sea and play Will for the win.
The difference here might be Meandeck Gifts versus other Gifts. In the old Flamevault Gifts you had Demonic Tutor, Mystical Tutor, Vampiric Tutor and Imperial Seal that could all grab Tinker for you. They can of course also grab other win conditions. Gifts is more of a late game Tutor and you can win quite easily without it.
Meandeck Gifts does not run many of those tutors. I think Steve's list did not run Vamp or Imperial Seal. The more common way to find win conditions is to actually Gifts for them. In this case I find Gifts players are better off grabbing a Tendrils enabling pile rather than a Tinker Pile.
On the play you keep a hand of Island, Fetch, Emerald, Mystical, Gifts, Force, Merchant Scroll. What do you do? Lets say you decide to go the Tinker route. You drop Island, Emerald and Pass. Now Uba Stax attempts to play a Smokestack on their turn. You have three permanents in your hand. You will be drawing a Tinker so you won't add to your permanent count there. Turn 3 you sack one permanent. Turn 4 you sack two more. You know your turn 2 draw won't add to your permanent count and your turn 4 draw is too late so your only chance to draw into a fourth permanent is your turn 3 draw. Does a deck that runs 25 permanents take that risk? What if Uba drops a Chalice @0, now your permanent count is even lower. You can counter Smokestack, but now you are vulnerable to a turn 2 Welder. It all seems risky to me.
I am interested in what people think the correct play is in the above situation. Would it be better to open with Scroll->Recall, Scroll->Drain or Scroll->Rebuild?
Regarding Rack and Ruin. Clearly I don't understand the card. I thought that if on resolution a target was illegal then the spell is countered. Do all of the targets have to be illegal?
