congratulation on your purchase--awesome

I have reloaded for a .470 recently and had great success with 89 grains of RL-15 with a 500 gr woodleigh--Fed. 215 primer--Norma brass--I also use a filler of 5 grs dacron --shoots very well in my double--

Personally I don't think you need to start as low as 84 grains --but hey,,that's just me

I agree you should use a chrono--very helpful in developing a load

Good luck and keep us posted

Ripp