Man, I play both sides so much it took me a little time to think about what side is generally "strong side" rubber guard. Most people in 10p play the same strong side as Eddie which is grabbing rubber guard with your right hand.
My experience is, since almost everyone you face will have very little experience training against rubber guard, your much better off either a. working on the side your coach shows it one (I guess Eddie on DVD's and MTS if your a ronin) or b. work which ever side you gravitate toward or are more flexible one. I would work to you strengths and not other peoples perceived weakness because if your working rubberguard at all, you are already training something most people don't work on defending much. Its not nearly as big of a deal as passing left for instance, which many people have a very lopsided amount of defense time put into it vs passing right.