First of all I will say the Goliath is a very good RTA that is in the mix of the top 5. I haven't had an RTA yet that didn't give me issues with heat transfer to the Mod. So IMHO the heat sink/dissipation fins would be better utilized on the bottom. I agree with removing them from the top in lieu of having the ability to be top filling (perhaps something akin to that of a YiLoong Fogger V6, especially with the juice flow control it has). I love the 6 mm chimney and think that if they were to adopt the aforementioned type of top fill they could go with SS threads set within Delrin that keep the 6 mm opening all the way through a removable Delrin tip (of course including a Delrin adapter to downsize it to utilize 510 tips for some who just prefer those). I would be a fan of having a true 4 ml tank capacity but also believe that maintaining a short chimney profile supports maintaining maximum flavor delivery (provided you have the proper coil(s), wicking, air flow, etc.). Additionally shorten the height of the lower SS band to make it easier to see the lower liquid level.
Now, my other suggestions will likely require you to have some vision:
Juice control – the length of the control slots (IMHO) isn't necessary so what I would propose would be to make them more precise in length and width to what would be needed in proximity to the juice channels and have the ability to be completely closed, one side open/adjustable, and both sides open/adjustable. This also would coincide with adding a third elongated air hole to the AFC band/ring to allow air flow to only one side. Now, with the aforementioned, you have the ability to be a single or dual coil RTA.
Air Flow/Direction within the base – Simply angle the air holes that are drilled in the deck such that you have air flow across the coil doing a swirling cyclonic action with the vaporized liquid within the chamber as it travels upward toward the chimney. This would require thickening (width) of the negative terminal area (actually while you're at it have the negative post milled out of the deck as a solid piece) and moving the air hole and one juice channel on each side. I would keep a thinner section of metal (where the air hole opening is accommodated now) for threads on each side. I even have a design in mind for the cap (funnel) to chimney piece that would capitalize on this flow pattern and make getting juice pops up the chimney to your mouth nearly impossible.
Sorry this post is so long… just wanted to put my

in. Now y'all have something from the backside of a horse...
