Man, that thing should be perfect before you pay for it and take it home. Once you've handed over the dough and taken possession you've lost a ton of bargaining power. It just becomes much easier for them to make excuses why they can't get done what you want.
We spent about 4 hours doing our PDI and they fixed everything before we took possession. They wanted us to sign the papers before the PDI but we made sure we did the inspection before.
It's hindsight now, but I wish we had known about the problem with the Chinese ST tires when we bought it. We would have made arrangements to have different tires, even if it cost some extra money.