When I worked with a consultant, I was shocked at the amount of time I spent (and by extension, the consultant) on communications and misunderstandings. Distance always increases delays except when you need alot of hands at one time.
I find Yo’s estimates are pretty safe. Although, remember that NPD is inherently variable and therefore difficult to predict. I can time a person screwing an enclosure together and by the 10th time they do it have a good idea of how long it takes. That’s simply impossible to do with a any accuracy in NPD.