Probably dumb question but--I bought Nicotine for DIY from a new vendor without paying attention. It's 6 MGs nicotine. The rest is PG. They sell it (I see now) in 6, 18, 24, 36 48, 60 and 100% MG levels. My question is this--for a former pack and a half a day smoker, what would be a good level...