Here's a recommendation from a long-time .416 Taylor owner, FWIW.

No need to chase 2400 fps. Period!

If you shoot the 400-grainers at 2250 to 2280 no powder compression is needed, the cases will last forever, the bullets will penetrate deeply and kill better, and that 9-pound rifle will not beat the crap out of you.

Remember the British .400 Nitro killed tons of DG over the decades with an MV of 2150 fps from the test barrel, considerably less from shorter-barrelled hunting rifles. Nobody had a chronograph back then, so no-one questioned the fact that it just worked!