I'm sure breast enlargement by pumping is possible. A while back, my massage lady who's more then aware of my ball pumping decided she would like her boobs plumping back up after breast feeding a while back. We had a look around and Noogleberry do breast pumping domes for various sizes of breast. looking on their forum they work but you have to be dedicated and everyone is different and progress at different rates. After deciding which size of dome she needed we ordered one and she made a start but didn't get on with it. She complained it kept losing it's seal and was uncomfortable. Unfortunatally, as much as she has no problem with me ball pumping and has seen me in the tube many times and naked on her massage table with the results, she just won't let me see her trying to pump her breasts to see if she's doing it right or to see if there's something she could be doing better. As i make my own ball pumping tubes that are fitted with a cushion seal i said i'd have a go at making one for her. The first one looked really big and after a while she passed it on to a friend of hers who would like some boobs full stop. It's probably much too big for her but i don't know. I made a second one for my massage lady that should be a better size for her but she's said that she struggles with it. With that in mind it's not getting used and i can't get to the bottom of it because she wont go topless in front of me.
I'm convinced however that they will work and a bit like Noogleberry, depending on how big you want you're boobs you may well have to step up the tube sizes as you go but with 2 tubes out there and a reluctance to let me see what's going on, or not, i can't promise that one of my tubes is any better tan any other, Bear in mind though that you will have to be consistent with it and keep at it until you have some increase in size. I'm afraid i can't be more precise as i don't have a pair of boobs to try it myself but i'm sure you can get bigger boobs from pumping. You can also re-shape you're boobs by pumping, Cowgirl is proof of that.
If you're interested i'm sure i could make you a tube although a measuring session would help. No good if you're nowhere near me though. i don't mind a PM if you're interested.