Thanks for bringing this thread back to the surface, Tracey. I was going to respond (Really!) but then got sidetracked, and forgot all about it.
I've grown a few different clones of the species Lilium lankongense for about eight years now. I don't have sandy soil, only clay based, with a pH of neutral to slightly alkaline. Though I don't think the lankongense are as happy as they might be, none have perished, and barring the occasional rodent munching, they get a little larger each year. For me in clay, I think the key is the right moisture.
While correct watering is much more easily achieved in sandy soil, it seems that it is not impossible in my case either. Cultivation is kept to a minimum, to preserve the natural structure of the soil that not only is beneficial to soil ecosystems, but also drainage. I'll never forget what turned out to be a happenstance experiment in my early years at this house:
The previous owners had a vegetable garden, sort of. It was the native subsoil clay topped with 4 inches of topsoil. Well, I wouldn't have that, and I began incorporating copious amounts of organic matter. It was the second or third spring, as I was waiting, waiting, waiting for the garden to dry enough to work, I decided to just turn over big chunks (shovelfull size) with my digging fork. Just turn over once, no breaking up, nothing else to damage the soil structure. This, in an attempt to expose more of the soil to drying.
Starting on the "drier" side of the garden, I worked about half way through, where I deemed it to be too wet even for the most gentle forking. Then I waited some more. In the end, the untouched wetter end drained and dried faster than what I had ever so gently turned over!
What happened? I severed the vertical column of capillary action that pulls water down through the soil. Ironically (and fortunately), this is the same capillary action that moves water up to the surface as the top soil layers dry too much. Isn't nature grand!
Well, I digress...
My point is that if clay is dry enough, but not too dry, lilies can be happy. Such a "revelation" has born out not only with L. lankongense, but also L. fargesii, L. szovitsianum, L. duchartrei and L. papilliferum.
But "dry enough, but not too dry" is a precarious high wire to walk. Go the easy route, and use sandy soil.
Somewhere along the line, I acquired Karen North in 2008. Was it from you, Tracey? Due to its hybrid origin, it is predictably easier to grow and more vigorous. Other than my own hybridized seedlings, I don't grow any other lankongense hybrids.
I did pick up some more garden sulfur today to sprinkle over my L. lankongense hybrids. 
