I’ve only used the stock (short) stem with the cooling unit. Indeed, I ordered an extra of each since receiving my Tinymight 6+ months ago. Can’t hurt to try a 3rd party stem (which I don’t currently own) without a cooling unit. Just start at low temp and work your way up if it’s palatable, that’s all. This vape is so versatile as we’ve all discovered. And it works all too well for me natively with the stock stem and CU, just the way I like it. OK, I did mate it with my glass rig once and it was great/fun with the stock stem and cooling unit, though I did crank up the temp then going through water. Cheers.