Quick nitrous fuel pressure question

Just a quick question. Ill be plumbing my nitrous system this spring and was just curious what my fuel pressure should be regulated at going into my nitrous fuel solinoid.

Ill be running a 100 shot on a plate.

Another question, how come I notice some have a one regualtor for both the nitrous and the carb. And others (like ill be doing) have one regulator for carb. And one for solinoid.

Is it safe to only have one regulator for both?