Trying to work up some loads for my No1 .450/400 NE 3"

I have the Hornady data sheet which gives some 400gr loads, but I'm struggling a bit finding loads for the lighter bullets using powders available in Australia...

I've got some Hornady .411" 300gr SP (originally for the 405 Win) which I think would be a good load for big pigs, Sambar deer etc.

All I can find so far is RL-15 data (64.0gr + Dacron filler for ~2100fps with a 300gr bullet) which is the same charge as the 400gr bullet... using the '75% Rule' so a double rifle will still regulate with the lighter load.

I'm after some full-house loads for the 300gr bullet which should surely get to ~2400fps safely in a No1?

I've also got some 41 cal .410" 210gr Speer pistol bullets for which 28.0gr to 30.0gr Trailboss is recommended. Could be a great cheap plinking load

All info gratefully received...