I am trying to develop a splitView based iPad app, that displays the split interface in every orientation. I have tried subclassing the UISplitViewController class as given
What you are describing sounds like Apple's Settings app (on iPad). My intuition would be that this is not a UISplitView. It's just a view containing two table views. Fix the layout manually when the device rotates. In other words, if you don't want what a UISplitView does, then you don't a UISplitView at all.
EDIT 12/19/2011: In iOS 5 the problem is basically solved, since you can now define your own container view controller, plus you can prevent the dismissal of the left view in a split view.