Being a gigantea hybrid, I'd expect it to be a really slow grower.
Deep shade and very warm is the best environment for the plant. In nature, gigantea will never see temperatures below about 73F, and while corningiana might see a few degrees cooler at times, you'd do better keeping it warm.
Keep it evenly moist, but watch that the sphagnum doesn't become to compact, as that will suffocate and kill the roots, are hard to replace on such a slow-growing plant. Feed regularly, but lightly - again, slow growing equals a reduce nutritional demand.