People were determined to make DIY vertical coils work, but after all the attempts, I think even the hardest of the hardcore will admit to it being a losing proposition...

I did have a couple highlights, after trying almost everything vertical...for dual coil, the MUTANT by Vandy Vape Stood above the VLS by Oumier and the 502. Single coil was the ALCATRAZ 22mm, with honorable mention to VapeWare's Nextera, which did it right SO long ago...

Airflow direction seems to be the problem...well, that and gravity, lol. I like saturation, and even with "cool" squonkable posts, etc, it just seems that it will never match horizontal coils in a RDA, as far as wicking is concerned.
Nextera and Alcatraz both had serious chamber reducers to direct the airflow, and that seems to be where their success lies. I'm not against someone trying again, but I think the writing is on the wall!