Depending on tire height, you'll run into inner fender clearance issues before the crossmember is bottoming out on the road. My '66 was static lowered with 215/75-15 tires and they scraped the inner fenders over bumps before the crossmember ever bottomed out. There was around 1.5" between the tire and inner fender, had to pull one of the fender bolts out to keep the tip of it from digging into the tread over bumps. With bags you can set the ride height higher though, and drop it when parked.
