It depends on the rat really. All my girls are fancies/top ears, and three of the four of them should be good in that 1.5in spacing (if I remember the spacing correctly). They're all rather pudgy girls though. Um, I don't know exactly, you may need to use your own judgement when you have the rat, as to weather they could get out or not. I'm not good at judging length/distance very well, sorry.
And Pet store rats are a bit of a discussion in their own right. All but two of my rats have come from pet stores (since the closest legitimate breeder is about three hours drive from here and my mom refuses to take me on that long of a trip for a rat). Most of them are prone to early diseases, and I have had a few that died of kidney failure and such at as early as four months old. On the other hand, I've had three that have lived, 2+ years and only gotten sick once (colds mainly).
If you don't mind the uncertainty of their health and possibly temperament, then you might not have an issue with pet store rats. I would suggest looking for breeders close to you though, that way you've got a better chance of having your babies for 2-3 years or longer. Then if that fails, look for rescues close.
If you live in an area like me though, you won't have any legit breeders or rescues within a reasonable distance, and you can only buy from pet stores or feeder venders.
And I feel like I rambled again, sorry.