My dry hopping technique has evolved through the years. Since you only do primary, I'm not sure relevant it will be, but here's what I've come to....after primary is finished, I cold crash the beer, then rack to a secondary. I add the dry hops, flush the secondary with CO2, and let sit at room temp for 4-14 days. Then I cold crash again, rack to a keg and carbonate. I used to dry hop in the serving leg, but I've found I prefer this way. It also seem to avoid biotransformation and hop creep, both I which I don't want.