imo if it hermies it's genetics not training. I train every plant unless I'm pheno hunting, start with super-cropping (multiple times if I'm vegging longer), then FIM all tops about 10 days before flipping. Have yet to see a hermie. I do try to give them 7-10 days with no stressful training before flipping, not sure if that helps but I think they should be as strong as possible before the flip.