does double flavor decrease vapor or clog the atty?
This is hard to give a simple answer to as it depends on several things.
First the atty clogging issue as it is easier:
1. What the flavor in question is made of, and what it is soluble in (water = good, oil = bad. (for atty clogging potential as well as potential health reasons)
2. Is the flavor in question visibly dark or light in color? A general rule of thumb is darker fluids may have things in them that might leave an atty clogging residue, where lighter colors typically have less to worry about.
On to the vapor concerns:
How much of a dosage a "single" flavor would be compared to a double and what you are using to mix it with, the ratios involved etc.
Some possibly technically incorrect examples to illustrate the point above:
If my single flavor dose = 20% , then my double flavor dose = 40%. And I will use PG for the remainder. I have only 60% Pg here, so yes I will loose vapor in this example, and may have a flavor that would knock down an elephant.
If my single flavor dose is 5% and my double flavor is 10%, And I again use PG for the rest, the loss of vapor is much smaller than in the example above as I have 90% PG left.
I loved the elephant killing 40% flavor, but also want more vapor so I attempt to give the first recipe more vapor:
I mix 40% flavor with 30% PG and 30% VG (using VG to give it more vapor) then I try it and see how it vapes.
If I am satisfied, I stop fiddling.
If I am not I can go back and try 40% flavor and 60% VG.
If that still does not work, I would need to look for a stronger flavor to begin with! i.e. more concentrated strength.