Not sure why the new #UISplitViewController iOS 8.0 goodness isn't inspectable, but this fixes it.

Inspectable UISplitViewController

import UIKit

@IBDesignable
class SplitVC: UISplitViewController {
    
    @IBInspectable var minCol1Width: CGFloat {
        get { return self.minimumPrimaryColumnWidth }
        set(newValue) { self.minimumPrimaryColumnWidth = newValue }
    }
    @IBInspectable var maxCol1Width: CGFloat {
        get { return self.maximumPrimaryColumnWidth }
        set(newValue) { self.maximumPrimaryColumnWidth = newValue }
    }
}