I was taught to slow down before tracks or obstacles you might have to cross (they used 4x4's in my MSF course), get up off the seat (on the pegs) and roll on the throttle just as the front wheel is about to hit the obstacle, this unloads the fork and lets the bike "climb" over the obstacle with less force, and only then sit back down. I do this every day with a set of rough at-grade tracks, and never take the lower back abuse. That said, the Rebel can bottom out pretty easy, even over a change in pavement, so some back loading is expected on this bike and in the upright riding position.
ATGATT - be safe!
1999 250 Rebel