Orchiectomy, what you call castration, does not make srs more difficult. All it involves is removal of the testes, and no skin is removed. Many SRS surgeons have a preference about where and how the incisions are made, which apparently makes it easier when doing SRS down the road, so you may want to talk to whoever does your orchiectomy about this. Every major SRS surgeon says that this does not make SRS any more difficult, so do not worry about that. If it's going to be five more years regardless, it's safer for your body not to have to take as much spiro and E for all that time as well.