I've tried to be diplomatic ,but honestly scarfed extentions for raising a building? A new post could be fashioned and installed ( and would be a better repair) . Scarfs are not difficult, but they are complicated and time consuming, and mentioned earlier some customers could care less about a masterpiece of joinery hidden in their wall. Seriously I'm interested in how you would cut the joint. Not where but what tools you would use to get 4 surfaces(that will be in compression) to align perfectly without shims? We do quite a bit of work for historic preservatiion here in NY and they indeed do want to preserve historic fabric, they are not cheap and indorse the bolted lap joint. I'm trying to find some photos of some sheared scarf joints, they do split if loads aren,t distributed correctly. I would not recommend scarfed joints as a normal post repairs. We don,t usually have the luxuarry of choosing every client, ya gotta eat. The're still great scarfs.