i've only topped one crop before and I waited till the leaf set with 7 blades... i just FIMed a batch too and did it at the same time... I'm bending some plants too and it appears that the topped and FIMed ones need a little longer. I'd wait atleast one more nodal set... but other than that try them out and see. you'll learn more by doing it that anyone of us can tell you... look into FIMing though, it looks like mine are doing better this way than the ones I topped