I haven't had a chance to fire it with the Bersa extension yet, but it does make the P-3AT a little harder to conceal in a pocket. The front edge of the extension sticks out too much in the pocket. I've got an idea for a pocket holster that might help, but the local Tandy store closed a couple of years ago, and I haven't found another local source for leather.
Guess it's time to check all the available P-3AT holsters to see if somebody is already making what I want to try, then (if I can't find a holster) check Tandy's website for mailorder prices.