It is mostly atrophic mandible cases where the LC floats. It has a lot to do with patient posturing. The texture is weird so the patient never really relaxes their tongue / cheek / lips / floor of the mouth. It also simply lacks the precision of a processed baseplate.
On an atrophic / flat palate upper it also makes a difference because you can put in a full luckman postdam. The difference in stability between that and LC material is huge. It doesn't matter for normal cases, but does make a difference in the marginal cases.
Thank you for the explanation. I can understand how a texture difference could cause patient comfort/reaction variances.
I've always put postdams in my l/c baseplates and a wax skin over the entire occlusal side when there is a rim instead of a gothic arch set. Could be fooling myself again, but I feel the wax skin lets them feel more comfortable, and have a better experience. As well as creating, psycolgically, a better, more denture-like look that creates less aversion to this odd thing in their mouth giving better results a higher opportunity percentage of occurance.
Edit:Next time a case with this issue comes through, I'll make 2 and ask the dds to give feedback, and see if he will provide some from thept as well.
re-edit: the import ants of proofreading.