You should have plenty of time to do a figure eight ride. How long did it take you to do the Orange and which direction did you ride it?
A figure eight:
From the mountainbike staging area (Pulaski Woods South) go south up the connector to the yellow trail, turn right (west). Follow that as it crosses the road, where it splits to the left single track (Brown Trail, Pipeline) or to the right (Orange Trail).
Take the Pipeline (Brown), to purple, to yellow, to Psycopath,
Psycopath to Turf. Ride Turf, make a right on the pavement section (Black) and go back up to the intersection where you entered Psycopath, via black, brown, yellow (basically staying right).
From there take the Orange trail through Three Ravines, One Day and up Gravity Cavity. You can take the connector from yellow back to the car(s).
Download and print this map as well as my instructions.http://cambr.org/TrailGuides/guideElements/maps/Palos2010Map.pdf