I have free state 12rd magazines for my 9c, and I have difficulty sometimes getting the 12th round in. I thought it was just me having difficulty getting the magazine into the firearm, after topping off the magazine. Sometimes it can take two or three tries before it seats.
Right now, I'm still only using 9rds, because I like the easier(faster) loading.
You should try the hack on one mag to see if it works for you.
I couldn't load 10rds at all.. It was like it was designed as a 9rd mag.