Fineline - What sort of changes clause do you have in the contract? It seems to me you have demonstrated due diligence, and that this development was not predictable, and should reasonably be able to negotiate a change order.

It would also seem that in the end, inspection will be far less costly, monetarily, schedule and aggravation wise.

I can vouch for TPI, they stepped in for us once when disputes over grade became heated and another grading agency bowed out, mid-situation, just to avoid the controversy. I also know of no other grading agency which will grade in-situ, and both historic existing framing, and "notched" timber.