Hey Roly,
I grew my dowiana with great success in a basket with coarse bark. That was in Hawaii, which has lower humidity and higher winds (5-25mph everyday on average). I watered every day and it dried out in a few hours. I would tell you that anyone growing this species in spag is nuts, but the fact that Ruben grows in spag in your area with success means that he probably knows something I don't, so he might be someone to listen to.
As for s/h, I would definitely try it with Catts. I started with s/h here in Texas and am having excellent success with walkeriana:
2 Catt. walkeriana's If walkeriana is ok with it, I would imagine other species that like to dry out (like dowiana) would do well in it also.