Wheyhey, at last I am learnign something!
So....This is what I think the order of drillinig should be, please correct me if I am wrong.
1. Drill pilot holes according to new stud layout. Use the appropriate size drill, same as the pilot drill on the Spotface tool.
2. After drilling, spotface the holes making use of the pilot drill.
3. Drill final holes, 14mm.
This method seems the most logical to me. The way I see it is that if the pilot drill is much smaller as the drilled hole, the spotface bit can still 'walk' a little?
Cheers!