I kind of did do that as my vape is a starter kit the nic i bought is pg nic so adding after should only lower the vg levelAlso when adding Nic later take into account that it will change your pg/vg ratio and depending on how strong you want may affect your flavour %
i.e. if you're making 12/18mg you would be adding around 15-20% more pg
Im trying some really cheap 88 vape liquid in my endura t 18 at 50pg/50vg sweet strawberry at 6mg nic and its not to bad
If i can make anything that tastes better than this then i will be happy