Hello, congrats on your new set up, its really great looking. I dont have a petri MOD nor RDA, so not familiar with it.
If its a Hybrid : meaning that it has either no top cap or a disc with just a hole, then you do have to make sure your 510 positive pin is protruding about 3-5 mm? Again I have no hybrids so not exactly sure of the safe amount that its supposed to protrude.
If its a reg 510 top cap , meaning it has a threaded 510 connection with an adjustable , usually brass or sterling plated pin then its just a standard 510 connection and the pin only has to protrude enough to clear the threaded part.
I found this photo that sort of shows the differences
This is a standard
Hybrid
I also found this that seems to sum up the do's and dont's of hybrids