Yes you could buy the full size mags and add the spacer but will be harder conceal if that was an issue for you. I dont care about consealing but im not that open with it either.
Here's my point though, if consealment is the question area, I would still be better off with the compact. 1) Shorter barrell, I know it's not much but it would still help. 2)Those times where consealment was a priority, I could always use the compact mags to cut back on grip length and still have my carry weapon. For all the other times, I can leave in the full size mags. If I bought the full size, I'm no matter what going to have a weapon that's at least moderatly harder to conceal. Still, the ability to conseal comes second to how comfortable the gun shoots. If I'm not happy with the way it feels, I'm not as likely to carry it. At that point, I'd just throw my wifes Colt Mustang in my pocket and be on my way.