D.J.
Hi D.,
I have a 5 month old son myself, who sounds alot like your baby! SAME exact story here. From experience with my older daughter though, I have found that if the nap is only 45 minutes, I sometimes let him go for no more then 10 minutes, because many times he will fall back to sleep on his own. I can't remember which sleep book I read it in, sorry, but it was referred to as the "45 minute intruder" because many babies wake up at this time in between sleep cycles. I've actually found it to be true for us in many cases. Most of the time he'll fall back to sleep for another hour or so.
Anyway, I know with my daughter at least, things regulated more as she got older. Have fun with your baby!!