Dipoles are designed for larger rooms than you originally placed them in.
However you are correct in the fact that without a rear wall you will more than likely have undesired effects mainly baised upon varying reflective qualities laying beyond the listening area. The point of a dipolar speaker is to help in the transparency of the surrounds in a larger space where the listening environment becomes dispersed. It sound like you new room is considerably larger and hopefully less square than your previous ht, my suggestion would be to utillize your dipoles and to change to a 7.1 setup, you will still have listening artifacts but depending on whats behind your theater space it will be less noticeable than using the dipoles alone in a 5.1 setup. Besides it's a great reason to move up to 7.1, just as long as the environment directly behind the viewing area is of no consiquence during use.
However you are correct in the fact that without a rear wall you will more than likely have undesired effects mainly baised upon varying reflective qualities laying beyond the listening area. The point of a dipolar speaker is to help in the transparency of the surrounds in a larger space where the listening environment becomes dispersed. It sound like you new room is considerably larger and hopefully less square than your previous ht, my suggestion would be to utillize your dipoles and to change to a 7.1 setup, you will still have listening artifacts but depending on whats behind your theater space it will be less noticeable than using the dipoles alone in a 5.1 setup. Besides it's a great reason to move up to 7.1, just as long as the environment directly behind the viewing area is of no consiquence during use.