Oh wow that's a big girl! So should I make the entrances smaller so they don't get used to swimming in there when they're babies?

I have a 1.25" diameter PVC pipe that runs through my tank and has 3 entrances. I'd like to know how wide peppered corys get to make sure they wouldn't get stuck in the pipe. Also, do you guys know how well they cab swim backwards if at all? Just in case 2 decided to go in from opposite directions ...