So I decided to do a simple test by using a plastic bottle with a psi gauge attached to the cap to measure the pressure for the recommended 3g of sugar per bottle. Also tested 6g per bottle to see what impact that would have on the pressure.
Here are the photos of the setup
The results were a little surprising. The bottle with 3g of sugar had a pressure actually higher than the one with 6g of sugar. But after about 10 days, I decided to shake the bottles a bit since I was wondering if the sugars were just sitting to the bottom and not really well mixed into the beer. It seems the CO2 was dissolved in the beer and once shake, the pressure on the bottle with 6g of sugar became higher. Later, both bottle were set into the fridge and pressure on both dropped, as expected. The maximum pressure registered was 36PSI for the 6g bottle and 30 PSI for 3g of sugar. Those same amounts of sugar was also used for regular 22oz glass bottles. So as a result of this test, I figured that 36PSI is not enough to turn the bottles into bombs and I could compare what carbonation levels 3g and 6g of priming sugar would create.
Here's a graph of the results.