How much is the bounty?
Will it pay out if I just tell you how it can be done?
It is pretty simple actually. Bribe some nodes by sharing some of the double-spend theft.
There is created an incentive to aggregate mining power in order to sell capacity to double-spend. It is an economics issue. Just because it can't be accomplished on the controlled testnet is irrelevant.
Rules are clear on how it pays out. Sounds like you've implied 51% attack, which is the same for many coins. Not trying to fud you, just not following. also not sure why you are duplicating your post in multiple threads instead of linking to one.