Congratulations on the fine regulation, Tinker. This brings me great satisfaction too.

Even though my Tolley .450 was regulated with the same charge of powder as yours (according to your barrel engraving), my regulating 'nitro-for-black' load is indeed 4 grains less than yours, ie 72gr AR2208 (Varget). Perhaps it is because I use the shorter case, ie .500/.450 with reformed shoulder, rather than the 1/4-inch longer .450 No.2 case.

Should I come across a source of 'inexpensive'(!) No.2 cases in the future I will put them to service and we can conduct a proper comparison!

BTW, it was awfully good of the Tolley brothers to boldly engrave the regulating load on their rifles, though in your case they were a little too keen with two conflicting loads!
Here's a reminder of the load details on my Tolley: