We will definitely leave this thread here for others to chime in if they have some experience with the set up you described. However, you might need to contact our regular Tech Support to get a better and detailed response on this. OSIsoft vCampus forums are mainly for programmatic questions and discussions.
Having said that, let me add that in general OSIsoft OPC interface is one of the most popular (if not the most popular one) interface out there. If you worry about the resources on the OPC Server box getting stretched thin, this would be the part that Tech Support would be in a better position to chime in.