With a modern 7x57 there is no reason why you should load it up a bit. The original 275Rigby was loaded with a 140gn to 2800 FPS. And a 7x57 should do everything the 7-08 does plus a bit.

I have had good results with my 7x65r and 173 gn h mantle bullets over 51gn of IMR4350. Complete through penetration on a100 kg (carcass weight) wild boar. Probably leaving muzzle at 2650 FPS. You can probably mimic this with a modern 7x57.