As HG said, your penis is primed and adapted at the beginning of the moderate pressure range. 5 inHg is the beginning of the growth expansion zone. 8inHg is the lower end of the upper limit. 10 inHg is where the upper safety limit is. Just by using 10 inHg for the first 2 minutes, you slam the door wide open for tissue expansion for the rest of the time.
The trick is to soften the tissues at the lower baseline that you have, which is 7inHg. On the second pumping, within that first two minutes, go up 1inHg each day to see what your barely above the comfortable pressure is, where pain should be just barely above the comfortable zone for your penile shaft. This is your new limit barrier breaker. After than first 2 minutes, reduce back down to the baseline. Notice I use the keyword "baseline" a lot. Why? That is your safety number.
As you progress, your tissues will continue to adapt. Just 2 minutes of that higher pressure will stop the body from adapting. I even test the unsafe barrier once at 16inHg using the water, and that's a bit no-no beyond 20 seconds. However, it was amazing. The inner tissues felt like it was snapping wide open for more expansion. I will slowly work up to 1 minutes down the road. However, the warning to you is, work your way up. Safely and efficiently.