This is the best time to move them and yes they are very forgiving. Here in zone 7 mine are setting buds and will be just behind Salvia Cherry Queen in first flowers which will open tomorrow. I would also suggest layering them in June since the layered branches are much more likely to survive the winter than older wood clumps.

Thanks for the advice about layering. I took a cutting from S. 'Ultra Violet' last year and it rooted easily.