well what happens if ya drop him into a spot and find out its sheet slate, having to use a bar to work every inch of the dig, a 1.0 dig can take a long time, i have found alot like this in wales , the quarry choses to sit under these sheets for dryness or simply becuse there sets have had to follow the contours of earth working thorugh the slate, i may be wrong but you can never know how long a dig is going to take, a 0.6 in slate can take as long as a 1.5 in an ash bank or sand, dont know any one who doesnt dig as quickly as they can but its the dig itself what determins the speed not the dog