Potty training pain

So, we've been working on potty training for a few months now. Nothing too radical, just putting my son on there every so often so he'd get comfortable with using it. While he doesn't mind sitting on it, I don't think he gets it yet. I'll put him on there, we'll be on it for about 15-20 minutes, and nothing happens. As soon as I take him off and put his pull up back on, he pees, poops or both. It's so frustrating.

Some other moms I know have done some pretty radical things to get their kids trained, including sitting them on the potty and refusing to take them off until they "performed," to punishing them with time outs or other methods when they didn't catch on right away. I don't believe in any of that stuff. While there are tons of books and advice out there on how to train, most everyone has one thing in common: you never punish a child while trying to train them. It will always come back to bite you in the butt later if you do. So I've been patient and reward him if he does perform with stickers for his chart. But those rewards are few and far between these days.

So.....

I've decided to try putting him in regular underwear with plastic pants over them to see if that helps. I think with pull ups, he can't really feel he's wet, so he doesn't mind continuing to go in them. I'm hoping it helps, because this is as radical as I'm willing to get with training.