I ran across a few websites about this, (it was months ago, so I don't have the URLs anymore), but the basic message was from all the priests that stated their opinions, it was more or less acceptable unless there was major harm done to the body or against teachings of Christianity. For example some of them mentioned that sex with members of the same sex, or getting into a threesome is against the accepted practices of the religion.

I actually read up a lot about this regarding Islam and BDSM (and for that matter Judaism and BDSM). With a few restrictions, as long as both the male and female find this erotically stimulating, it's encouraged since it brings the couple more intimacy.