Small Pbass grow at about an inch a month. They start to slow down around the 8"-10" mark. Once they hit about 6" you don't have to feed them as often, so that will slow them down a little. But small ones are very fragile and need to eat many times a day!
4 AT 10" IN A 75...? I wouldn't get any...
If you get them at 3" you will be fine for about 6-8 months TOPS.
My logic is... if you don't have a big tank then don't get them. They don't show good coloring until they get big so its dumb to grow out small ones and get rid of them... its just a waste of money...