You should really be aiming for having just one responsive skin that caters for both mobiles and more traditional desktop systems. Tis the way it's all headed and all that.
Whats the crack with the mk4 forum @Tabs ? doesnt that have a separate mobile skin?
I believe that the next version of SMF (2.1) will be more supportive of responsive skins. The problem will be finding one or making one that looks like this one....
IPB 3.x has a separate mobile skin. However IPB4.0 will ship with one single, responsive design skin which I think we'll likely use across the entire site when we upgrade.
You only need to look at your site stats to see the device breakdown and how it's swinging toward more mobile browsing habits. One of the reasons why tapatalk is so popular.