Either the % is capped at the old 20% or I need some other formula for getting past this barrier.
Best I've had is 25.9%, which slowly dropped as the population increased. This was on a society level 1 planet for an inactive person, so was only getting population increase. Currently at 22.2% for 35 Subspacers heading for a society level 1 planet with 63587 people. Still a few days before it arrives, so (if I remember) I'll let you know what it gets to.
How can I move Steel from all my now colonized planets from arcs - back to my main planet?
Merchantmen from your main planet and send them out to colonised planets. Or you can build scouts on the colonies and scrap them on the main. I think scouts are the most steel:people efficient way to move steel, but I could be wrong. Obviously that moves population too, so don't do that if there isn't a large population on the planet already. I'd recommend using merchantmen from your main planet as you probably don't need all that steel immediately and the merchantmen will make you some Quatloos too.
You could also just leave it there and build a few arcs on the colony when it's ready.
