Leaf clipping, by triggering a "damage" response, does encourage root growth. I would suggest waiting for the leaves to grow larger, so that they recover more easily from the loss of leaf surface (loss of photosynthesis) that is the result of clipping.
There is a point at which the leaves suddenly begin to multiply in number and grow dramatically in size. Clipping at this point prevents them from shading their neighbors, while also causing the roots and stem to thicken.
Bob
Looks like I have been transferring them to soil too quickly. I never wait for them to grow this big because I thought my weather should be fine. No wonder my field mortality is high. I will try to be more patient after this.