If you want to perform stellar manipulations after you've built the system gravitational shield you will have to scrap it, then rebuild it. Probably the safest thing to so is built one on another planet to within one turn of completion then halt the queue. Scrap the existing one and perform whatever you wanted to do, then release the queue and let the reserve facility finish building.
[ June 09, 2002, 19:59: Message edited by: Baron Munchausen ]