Peter, you will be fine. The Obsethed with the marker duke/baron is a really popular combination, and I've seen a lot of people with that setup. Rocker in firm conditions isn't ideal because you have less ski contact with the snow. However when skinning, the area where you generate the most traction and grip are form the last 3/4 of the ski anyway, so tip rocker really isn't that big of an issue. The obsethed has some rocker in the tail, but not a lot that it will really affect you a whole lot when skinning. Also, if you are skinning, you're probably doing so to get to better, deeper snow in which case you will appreciate the rocker, and the alpine binding feel of the baron on the way down. It's a good setup. Enjoy it.

I agree with Shane. I've never had AT bindings on anything other than twin-tips, and now some with rocker. It's less surface area for the ski to make contact with the snow on hardpack, but in pow conditions, you'll be just fine.

They will work, and twin tips are not ideal but I do it, and so do lots of guys out there. I say go for it.