Well, with 4, as long as you're just floating the hypothesis rather than attempting a Pascal's Mugging and claiming you have knowledge from outside the Matrix that this is true, we have no evidence at all indicating it's more likely than the equal-and-opposite hypothesis that it causes 3^^^^3 negative singularities - this probably also applies to 1, but not 2 and 3, it seems if they have extreme outcomes they're more likely to go one way than the other - even considering that they might somehow produce FAI, it's more likely that they'd produce uFAI.