I wouldn't be willing to exceed 32.0V for an 8s pack without balancing. If you have extreme confidence that charger is terminating at 29V it could potentially be fine, but that's a huge capacity hit to 18650s that are capacity rated at 4.2V/cell.
I really don't think there is a safe way to charge 8 18650 batteries in series. Charging two in series on a radio at work we had to carefully balance the battery resistance of each pair to charge them safely.