BB..........any particular reason for your preference to the 411 bullet, with so many new and great 416 bullets on the market now, it would seem to be a better choice. The 416X300 WM is a great cartridge with gobs of relatively cheap brass available (same goes for the 411 though) and it will add an honest 100 fps to the Taylor or do the same at lower pressures. You could use 375 H&H brass, 416 Rem brass, 458 Lott brass or even 8mm RM brass if you happen to have a bunch. I found with the Taylor that the necks were quite thin using 338 brass and 458 worked much better for neck tension, particularly after annealing, so I wouldn't recommend using 300 WM brass necked up that far.
The 411-338 WM would, for all intents and purposes, be a 416 Taylor or 411 Taylor if you like, with identical ballistics with equal bullet weights.