FSX Contrails & Max Temp

Hi all,Dose anyone know off the top of their heads what the ranges are for setting the temps for contrails to appear in FSX.I've read in posts that it's up to a max of -30 while others say -50. I've been doing some experimenting and use ASE for the weather input and I adjust the FSX settings using Markus Brunner's utility. I have not seen consistant results in FSX, I've set the Max to -49 which on this day equaled about 34000ft but noticed contrails developing around 25000ft which was much hotter that -49. What's the SDK say?... is it based on actual OAT at altitude which will vary day by day or is FSX using the standard international rate (ISA) of roughly 2deqs per thousand feet.I have ContrailsPro_1.03 which is great but I'm trying to make FSX do things a little more realistically which may have been the intent of Microsoft, that is to make contrails appear when its really cold and not apprear when its hotter up there like in the summer months.thxIM2