Thanks, Sero!
While I did spend considerable time developing the juice, it's probably more ad hoc and arbitrary than some people might assume. I don't have the patience to make 100 different betas using many different kinds and brands of flavoring. I do have about ten versions currently, but I settled on a limited set of flavorings early on, and the current versions vary mainly in mix percentages.
Once I've moved on from a given 6ml beta version, I tend to mess with it by adding other flavorings just to see the effects, but then I pour that into a larger bottle with all the other previous versions. Curiously, my 50ml bottle of "Junk Skydancer RY4" is my personal favorite of all right now, but I can't replicate it.
Lorann Naturals Creamy Caramel flavoring may be the "culprit" in your wanting a more focused caramel. The Lorann's might have more of a vanilla flavor to some palates (your among them), although I agree with the hangdude's opinion that Skydancer RY4 v2b is caramel-rich, with the vanilla as a trailing flavor, so your categorizing it as vanilla-rich isn't how I taste it. My newest versions (6a and 6b) provide the caramel and vanilla components from a combination of Lorann, Capella, and Nature's Flavors. I don't know if you'd like v6 more or less than v2b, but v6 is slightly less rich.
The only reason that there's any marshmallow at all in the recipe was for the sweet-sour counterbalance/contrast. The problem I've discovered is that the marshmallow develops and expands with steeping, while the citric/malic acid of Lorann Tart and Sour is very strong at first, when the juice is freshly made, but diminishes almost to vanishing within a few days. As a result, v2b started out with considerable sourness, but now has almost none. I haven't solved that problem yet. Maybe I'll try just leaving out the marshmallow. I'm trying to resist turning my home into a science lab or production facility. It's hard enough just recording every tiny change in each version and keeping track of it all. LOL.
The nicotine used is Wizard Labs regular 100mg/ml 50/50 PG/VG. I wanted to try John's Ice formulation, but missed out when it was available, and now it's gone, at least for awhile. I agree that the 250ml bottle of Wizard Labs liquid nic I used for this batch (I have a new unopened 250ml bottle and will buy another soon) has one heck of a punch at the 18-24mg level, substantially more than any of the other four brands I've used in the past.
I respect the true pioneers of NETs and consider myself an admirer and aficionado, but not at all a compatriot to those people. I'm just following their lead as an enthusiastic amateur. As I've written many times, I have no wish or intention to become a vendor or juice supplier. I already have a profession that I've loved for 40 years. This is just for fun, and to share with my ECF friends. I'll probably charge a bit more if I do another batch ($5 for a 10ml bottle sounds about right), but all I hope to make in terms of dollars is enough to keep buying flavorings, liquid nic, and PG/VG. LOL.