Last night laying in bed I remembered that I have the FasTrack graduated trestle set. So this morning I pulled it out and set it up under my loop and ran the BB nice and slow.
Since the track lives on the carpeted floor and kids are running around, most of the pieces of track are bowed, and you can see that as the locomotive travels on the track. Sometimes the rear engine wants to climb out because of it, but the front engine pulls it around. The noise on the climb up is the rear engine falling back on the rails. Otherwise the locomotive handled it just fine. The tender on the other hand didn't ride very well. In fact after I finished the video I kept increasing the speed to see how it was going to handle it. At one point at the top the tender popped up and the rest of the train rolled backwards as the couplers came apart. So I think with smooth transitions it could do a 3.5% grade on a O72 curve just fine.
