... Side note: i tested a mix quickly with only the following (did not use the pre mixed base)
Sweet Mango (CAP) 4%
Koolada (TFP) 2%
Ended in 80/20 vg/pg (did not add nic)
No harshness at all, so now im thinking there may be an issue with the nic in my pre-mixed base i purchased?
Sounds like you just have some Harsh Nicotine Base.
Here is something I posted Yesterday in a similar thread...
Making an Unflavored batch at the Nicotine Level that you Normally vape is the FIRST THING Anyone should do when they receive New Nicotine Base.
You have to know that the Nicotine Base tastes OK before you start to do any Recipes'.
It's like if you bought a Bottle of Rut Gut Tequila. If the Tequila tastes like Gasoline, wouldn't every drink you make with it Taste Bad no matter how you Mixed it? Or what you used to Mix with?
If your Nicotine Base, PG and VG are OK and relatively Tasteless, then you are Good to Go. And if you Do a Recipe' and it tastes Harsh, you can Rule Out that it was coming from the Nicotine.
So then you Look at things like How Much Nicotine is actually in your Mix? Or How Much Flavoring you are using?
Note: It's Much Easier and Less Confusing to work with things when you work in mg/ml for Nicotine than it is to work with Nicotine as a Percentage of 1000.
Note 2: When you get New Nicotine Base, and want to Taste Test it by diluting it down to a Vapable mg/ml level, you Don't need to Mix it and then let it "Steep" or sit for awhile. Just Mix it down to a Vapable Level and vape it.
"Steeping" is Only needed when Flavorings (or some Sweeteners) is used.
Note 3: Be sure to keep Detail and Accurate Notes on everything you Mix. Or if you Change a Recipe after it has "Steeped" by adding or subtracting something.
The Worst is when you get something that Tastes Great but you Can't remember if you Added more Strawberry and Less Peach? Or was it the Other way around?
You'll get this Straighten Out. And I predict that you will have some Nice Flavored e-liquids in less than 2 Weeks.
If you are Starting off with Harsh Nicotine Base, it can be Really Hard to end up with a Smooth mix. Especially a Smooth Fruit Mix.
Sometimes harshness can be counteracted using a Sucralose based Sweetener like from the Flavor Apprentice (TFA).
I'd shy away from using Hot Water IIWY. Just give your bottle(s) a Good Shake for 10 Seconds or so. If 10 Seconds of shaking Doesn't do it, probably nothing will.
Like I said in that Other thread, sometimes a Harsh Nicotine Base can be Salvaged by adding some Sucralose Based Sweetener like TFA Sweetener.
Unfortunately, sometimes it Can't. And the Only real option is to just Toss It. And to start over with some New Nicotine Base.