My suggestion would be to hold back on any major pruning until the plants are better established. And when you do prune, only cut back by about half. This will encourage the development of stouter stems that will grow up straight and be better able to support the heavy flowerheads. You may be looking at a couple of seasons before the curly or crooked stems can be safey removed without more weak growth being produced.

I'd also suggest you wait until mid to late spring to prune, rather than doing in fall or late winter. Stems that have been allowed to go through winter have ripened or hardened sufficiently to be more woody and less flexible.