Re: Drivechain critiques by gmaxwell revisited, maybe you changed your mind?
And FYI, from a game-theoretic perspective, it is a hell "harder" to steal a penny from sidechains compared to the mainnet. Double-spending is a covert operation and mainnet full-nodes are absolutely blind about it, but sidechain full nodes will detect the theft at the moment it is happening.
The full nodes would reject invalid transactions, and/or the blocks that contain them.
Newbies, if two transactions spend the same inputs, in the same block, then both will be rejected. If the other one makes it to a block, than the other, then the first one is accepted, the other rejected.