i dont have a saved game with a stellar construction in it right now, so it will be a while before I can try this. It occurs to me though, when you build a RW/SW it replaces then star in the system with a planet type RW or SW from the planet types file. this means there is no more star in the system. could you then use stellar manipulation to create another star and build another stellar construction? if so, you could park 33 construction cruisers over a star, time them to finish building one turn appart, and create 3 ringworlds within 3 turns of each other. wow.
then if you just moved your entire imperial population to those worlds and opened 10 wormholes on the same sector, what more would you need? talk about impervious defenses. once you had 11 of them you could build all the starbases directly from ground based shipyards, and you could see how fast your could induce a range check error by having 226 planets in the same sector. that would sure be ugly in tactical combat. yow. then if you saved that map and entered it into the TG contest..