Email alliant they will give you recommendations for loads with that combo. You need a lot more data for quick load most guys that run it may not want to give out the info for safety reasons.
Thank you to those that responded. I now have enough data to start safely working up some loads.
Barnes had not tested and did not have plans to try RL23, but they had recipes for RL26 in 270 Win (awfully close to a 280, no?) that were a useful source of starting information...