I have mine in a net plastic pot as well but I haven't treated them to that much cold weather. I'll try that this time around. In the past I've left armeniacum, villosum, esquirolei and a few micranthums out all winter except for one night. That night it was threatening to reach the 32-35 F range, chicken, so I brought them in!
This past January while in California for the Paph Guild, Jay and I notice the commercial greenhouse growers really didn't heat their places and it was in the low to mid 50's F at that time. I finished out last winter with low over night temps and I'll repeat it this winter. Lowest my thermostats will go is 50 F so I'll set them there. Not confy for me but the plants should like it.
Awesome tigrinum! Great culture! I'm trying this species now and growing it like Cattleya. I'll be sure to cool it down this winter -- that won't be a problem