@WVduckchick has been using it in her Janoel knockoff, with success and they are plastic, so I know it can work outside of the styros. Brinsea runs so well at 40/45% that I wouldn't see a need to try it in those unless I was having awful hatches and that would just defy the statistics of incubating in a BrinseaI have hot and cool spots in the Brinsea as well. I set the temp to a 99.5 average, then rotate the egg tray every time I add water. I'm still curious to hear if anyone has had success with lower humidity in the Brinseas or RCOMs. Seems like that only works in the styrobators, and the Brinsea users are shooting for 40-45%
