I have an LC9 Ritchies leather IWB for EDC CCW for a year no problem. I read in another forum that with some holster makes there have been mag disconects with the mag extention installed. I Do have the extention installed and no problem.
I have a Galco Kingtuk and have a similar problem with a different firearm. I think if I had the Crossbreed supertuck it would cover the mag release better and likely not depress it effectively as it does when I sit down with the Kingtuk.