As you guys know I'm pretty new at reloading and am currently working with my 275 Rigby (7X57 Mauser for you ordinary types), 24" Douglas barrel on a trued VZ24 action. I'm shooting the 154 gr. Hornady Interlok and currently using H4350 powder. I worked up a series of handloads from 42.8 grains, 44 grains and 45 grains. Hodgdon manual maxes at 42.5 grains and Lee goes from 43.6-49 grains, both with a 160 gr. bullet. These are four shot groups with each load, I also shot my normal S&B 173 gr. load. Temperature was around 90 today , wind 10-12 quartering from behind, haven't checked the actual humidity but damn did I sweat. Chrony was about 8' in front of muzzle, and I didn't even shoot it once.

S&B Factory Load:
173 gr. SPCE 2413 FPS, best 4 shot group about .9"

154 Gr. Hornady, H4350 Powder:
42.8 gr. Avg. 2438 FPS .862" group
44.0 gr. Avg. 2454 FPS 1.2" group
45.0 gr. Avg. 2513 FPS. .908" group

I'm still 4 grains below the Lee maximum, no signs at all of pressure problems, I had an experienced reloader look at the primers and he also thinks they show no pressure signs, no heavy bolt lift etc.

My question is, should I continue up another couple of grains to see what the groups look like or be satisfied with the current velocities?

Thanks for your opinions.

No, you cannot increase the load.
You must handload for 20 years, before you can upgrade your handloading license to overloader.

Also, 51,000 psi SAAMI max for 7x57mm is all that the brass and VZ24 action can take:
a) 7mm brass lacks the subtitles of design and heat treat of the 65kpsi 270 brass.
b) VZ24s are notorious for being good for 51,000 psi, but not 51,001 psi. The ridiculous gas venting scheme sends hot gasses into the magazine that can set off the ammo creating a chain reaction affecting everyone's magazine at the range and invading the gas tanks in the parking lot, which in turn could end the world. You can't be too careful with that hanging over your head.

And then there is the engineering that goes into every Hodgdon published load.
No lay person can understand the science that goes into making a "not to exceed load".
It is similar to Werner Heisenberg's inventing quantum physics.

Well now you bring up another interesting question, Hodgdon only goes up to 45,400 CUP, Lee's loads go to 48,500 CUP. Now I know that means copper unit pressure, but can't find anyone to give me a formula for converting CUP to PSI. Is that similar to string theory?

From looking at your results you may want to try 42.6 and 42.4 grains and see if the groups get even tighter.