Can crown be ground to fit opposing teeth?

I recently had a root canal and crowning of my upper left molar. The problem is that it grinds against the opposing teeth. He made some minor adjustments while fitting, but was not enough. He suggested to grind a sharp opposing lower tooth .02mm. I was against this, as natural teeth are precious. So, how much porcelain thickness does he have to play with? This is metal on the inside, porcelain on the outside. In the extreme, how hard will it be too take out the crown? Thanks!