That also occurred to me Martin - after all, a couple of days is not gonna make a huge difference in the grand scheme of things. But these layers are small by my usual standards - only 2 yrs growth, and I also recall successfully doing small layers without rooter in the distant past.
Taken with the above advice, I'm fairly confident this will work. But as I'm running behind schedule, I might only do 2 now, and the other 2 later with the rooter. At least then I can be assured of 2 out of 4. If the worst happens, I will have to 'sacrifice' branches from the top of the tree.