Re: Propagation Times
Yes, I consider equal propagation times in both cases, even if the propagation time through an inner trace is a little bit higher than on outer ones. The difference is not semnificative. But this issue is dependant on application. For example, if I have to route a high speed ECL differential clock signal from one point to another, the propagation time itself is less important (it is important relative to other signals or clocks), it is more important to minimise the skew between those two traces, and this is done by keeping both traces lenghts equal. Often (and also it is recommended), both differential traces are going on the same layer, so there are no inner/outer propagation differences from this point of view. But as I said in the previous topic, if you really need exact results, you'll have to measure it.
/pisoiu