Feat here, happens in Green Lantern Vol 4 11. Guy and Hal fly from Sector 0 to Sector 3600. Sector 0 is in the center of the universe. So, they roughly traveled 4.4e+26m, the radius of the universe. I know there's a statement about the universe being trillions of light years, but idk if that's a one-off statement or of t's consistent.
Timeframe is about a few hours. Hal had a dream in this period, so I'll assume 3 hours.
4.4e+26m / 3 hours = 4.07407407 × 10^22 m/s
135,896,484,093,672c
However, this was done while they were hibernation mode, and shouldn't scale to their man stats.