The regulator on the valve is a little redundant. Check this out yourself (Google), but your natural gas line should be regulated to about 7.5" WG (water column). You'll be passing 7" to your burner.
You could test the regulator and set it precisely with a Dwyer Magnehelic gauge. (Google search again) or just roast a pound of beans and see what happens. I'd shoot for 1st crack somewhere between 6-8 minutes?
More experienced Sonofresco guys, feel free to chime in with your times.
If you are significantly out of that range dial the pressure up or down accordingly.
I would probably drill that hole to make the whole process easier than tearing the machine down repeatedly to adjust that spring.