Frame Rail Connectors

I agree lots of stuff gets overthought. That said I've seen a lot more than 1/16" movement when a car is jacked up. Not surprised there's little movement on a rotis since the car is likely stripped right down.

I'd think in terms of what's fairly easy to do that can buy you some peace of mind. If it's just as easy to put them in later when the car's on its wheels, do it then. If not, and its easy to get it supported right, do that. Just remember once they're welded in you won't want to take them out.