I know the rules said 1 single optimal GonG connector, but I, as a pretty much guaranteed future owner of your product (since my vape obsession is in full swing right now!
), would prefer separate 14mm and 18mm GonG adapters. Here is my reasoning for this ...
So ... based on that and my overall opinion on the matter, not to mention when you consider manufacturing costs and the fact that people will want a GonG adapter but will not want to pay exorbitant prices for it .... the best option is a simple straight stem to replace the current one with 14/18 options
if it really needs to stay upright while in use and someone wants to use a standard bubbler with an upright connection ... than they could easily enough make use of a small silicone tube to connect the GonG adapter in question to the stock Ascent stem.
Edit: I know this is not the most creative option, and I regret that; but I still do believe, in this case, that it is the best, and most desired, option by most customers.