PAllen: Hmmmm... if I understand what you're saying (and I'm not certain I do!) you mean to say just do the velocity addition anyway? I'm trying to find a way around that part. As I said in my original post, I want to be able to show that v=d/t works in the rest frame, the 0.8c frame, and the 0.4c frame as long as we use the properly framed d and t values.
If you are saying I could do this, could you elaborate on which transforms you are talking about? Do you mean to say use: