Have any of you looked at the Agricultural part of the 1851 census? I just did and found that it names the concession and lot number and number of acres for each owner. It seems to me that this is helpful in tracing the land transactions. For example, in my Grant family, Cons. 2, SSRR lot 15 is divided between James Grant (W 1/2) and Ann Grant (E 1/2). James also owns all but 15 acres of W 1/2 of lot 16.
This provides almost a mid-way point between the original land grants and the 1879 plat map.