Vikings: Yea, but that would defeat the purpose of "hiding" your opponents pieces. I mean if you know you can't move a piece to a certain place, then you would know where at least 2 of your opponents pieces are. (And with a lot of trial-error before you submit, you could learn a lot.)

I think if there was going to be a "dark backgammon" version, then if you place 1 or more of your pieces on a space that already has 2 or more of your opponents pieces, then your pieces should end up on the bar. Then you will only know after you submit of 1 place where your opponents pieces are, and lose position because of it.