He still wouldnt have odds to chase if i bet half the pot, but he would be much more likely to call that bet. why not force him to pay as steep a penalty as possible instead of worrying over the bet size that just barely takes away his odds?
This is true, if villain will call badly for 20bb AND he'll call badly for 40bb, obviously pushing the larger is better.

However when we get into the realm of big overbets, the most likely thing to happen is that villain will fold for the first one and after that he'll start nutcamping you. You have to make sure the amount of times he folds plus the amount of times he calls and you suck out will pay for the few times he calls and you *don't* suck out. The times he calls when behind just don't even matter in this discussion. Those spots are ALWAYS +EV and of course the more money you have on the table when villain makes a bad all-in call the better. Thats the easy part. Its the other stuff that gets tricky and is really the crux of the strategy. I'm not sold that with a 70bb strategy villain can't just nutcamp you.