Crinum calamisteatum can grow nicely in quite low light - it does like a rich substrate, though (=root fertilisation). This species of Crinum does have significantly smaller bulb, than C. natans and C. thaianum - looks more like a "thickened stem" actually.
As for your problem of keeping the plant anchored, I suggest you gently tie a small piece of rock to it, in such a way that the rock will "hang under" the bulb, roots spreading around it. Preferably use some thin cotton-line, that will disintegrate in time, so the growing bulb will not be limited by it. You then plant the Crinum with the rock buried and about 1/2 - 2/3 of bulb buried. Remember to add a fertilisatin capsule right under the plant.
As mentioned, your Crinum will likely focus on creating a good root-structure, before doing much noticeable leaf-growth.........the first is needed to promote the latter.
In general Crinum calamistratum is really a very easy and tolerant plant - but can be a slow starter............
Edit: He he - just a bit late here.......
