If you don't have to cross multiple joist bays, and if you can keep it down close to the ceiling, it's not too bad. The insulation above the pipes and the close proximity to the ceiling should keep them somewhat temperate. Being virginia, it can get quite hot in the summer which means that your cold water could be quite warm. Keeping it below the insulation near the ceiling should keep it from freezing, too. This will make adjusting and keeping the shower temperature a really tough, frequent endeavor until you've moved all of the water warmed by the attic out, then your shower will get colder. Suggest you consider a temperature controlled valve...it will be better at keeping the shower temp fairly consistent.