Hello
Weighing all the principles throughout the Word of God regarding sex, nakedness, and covenantal marriage principles, I would suggest that the weight of Scripture does not encourage this kind of activity. One: Sex is a covenantal act between one man and one woman at a time. Two: Nakedness is only encouraged between covenantal partners (two women are not in marital covenant with each other - only with the man). Third: Since sex and nakedness is encouraged only between a husband and a wife based upon their marital covenant between each other, the marriage covenant is being compromised. My goodness, next someone will encourage the children to be in the room watching as well (I can hear the argument now. Scripture doesn't forbid it, you know!? I would say that the principles of Scripture forbids this activity as well).
If one is going to error, I would suggest that one error on the side of purity, not on the side of "how much can I get away with"!