Rob,
I am not at all surprised that you have noticed something that grows better in sphagnum. I am no saying anything ill about the mixes, just making a side-comparison.
I germinated some Drosera cunefolia once, some on peat/silica sand, others on milled sphagnum. The plants in sphagnum grew five times the size of the peat/sand plants in a six month span. The problem I have noticed with Nepenthes seed in milled sphagnum is heavy fungus attack, even when lightly misted with Benomyl upon sowing. This may have been due to unviable seed to begin with.
Sphagnum should grow in your highland greenhouses. The long-fiber stuff and perlite can both be mailed, as they are considered sterile, soiless components. I know you don't trade, but maybe you ought to trade those plain, green sanguinea to an overseas nursery for these products, lol.
Yeah, I know. Eventually there would be so many floating around that people would be saying,"These came from Borneo Exotics? What is Cantley doing? Sucking the pigments out with a straw?" Oh well.
Regards,
Joe