I ended that game by blowing the quasar, causing a chain reaction expected. The local supernova destroyed everything but the ringworld and the 4 big ships. The ringworld's shields were barely scratched. Also I noticed that: once you have a ringworld built there is no more jumping to that star as far as I can tell. Every time I try right clicking on the star, and from every angle, I get the ringworld right click menu. Before you build your ringworld you might try pinning the star to the UI, and try right clicking on the star that way. Maybe set the star to a control group.(This game has those key bindings right?example: ctrl+1 binds a group of ships to the 1 key?) I haven't had a chance to try any of this yet, I don't have a save before I built the ringworld. In fact the only save I have is after I blow the ring world with dsm, so if I want another one I'll have to start from scratch.
This game was a vs. 4 hardest AI; 75 star system map. I killed the last AI by 5 hours in. I reached the tech for ringworld in about 6 and 1/2 hours, I almost had enough resources to build the ringworld by then too. I have a much better plan for how to best "download" the ringworld next time. My next plan is to play a game against 8 hardest AIs on a 150 star system map, so hopefully mid-late late game I will get to use the ringworld, and in a practical way.