Just after topping them at the 3rd node (after it has grown out 6 nodes or more). Form the base of the manifold. Then, let them grow out again to 6th node, top down to 3rd node and strip 2nd node only! I blew it here, I stripped nodes 1 & 2...so I will only get 4 colas per plant.
It is hard watching the ladies bent over like this but it IS for their own good, and mine!