I may have missed it when reading this thread, but since you're using the upper cannelure have you verified that the data you're using was generated using the same cannelure?
If you use near-max load data generated using the lower cannelure (longer OAL) and then seat your bullet deeper to the top cannelure, pressure will be much higher. If they don't mention which cannelure was used in the load data, they almost always include the OAL.
You may already be aware of this, but I thought it was worth bringing up since I hadn't seen it mentioned. Lots of new handloaders scour these forums so it's good to specifically mention these issues.