2 has been discussed quite a bit. SFMM restricted the rocking/flipping which had the unintended consequence of inflicting uncomfortable forces on riders. Meanwhile the ones in Europe rotate more freely.
i rode it before they put those huge weights on. unbalanced and was continually thrown into and back into the seat. head and body trauma. i'm guessing my friend and i got the worst ride you could get. the possibility of getting a ride half as bad as what i did kept me from every riding again.
i still say that while i'm sure many enjoy it, the fact that there are only 4 total in the world says a lot about how parks felt about it if they thought about buying one.
If I recall correctly, the weights were there from the beginning.
The photo with the added guards is somewhat of a red herring as they were just guards and while added some weight, the main change lies with the ride settings.
The ride has settings that manage the spin resistance, and the park cranked them up around a month after opening. It's very likely that the main reason they did it was actually to increase capacity (although this was still the park's fault entirely which I will get to). When the cars came into the station a certain way after substantial flipping, the ride ops had to call for maintenance to come "right" the cars as the mechanism would sometimes "right" them to the upside-down position. This would cause a shutdown of 10+ minutes every single time while they waited for mechanics to show up and simply walk over to the end of the track and manually right the cars. I rode this ride 36 times in one day (I know I'm crazy) back before they made the change, and I can say they probably called maintenance at least 5 separate times to come do the same exact thing, causing major downtime for something very simple that should have been able to be done by the ride ops. I'm not sure if this was due to the lack of training given to the standard ops, as I understand that the ride ops at Grona Lund and other Zac-spins handle this just fine. Either way the park blew it.
I think it's very unfortunate as imo the intended ride experience was fantastic; I won't forget being put on with a large male and two tiny kids on the other side, and spinning ~13 times. With the same setup but post-changes, that might still equal 0 spins and a ton of pain. RIP Green Lantern.