Hi Jonny, sorry i haven't checked on the thread in months. It's good to hear you found all this interesting. I still reckon 4 hrs after smoking might be pushing your luck (not to mention that we are probably always more impaired than we think) but a lot depends on individual variables. Like I said somewhere above, if you only smoke a joint once a week on Saturday night, then you ought to be ok on Monday morning, but if you smoke everyday, then the THC deposits in your mouth are going to build up and take longer to dissipate.
If anyone else is still reading this thread and driving within the law matters to you, I would again recommend buying one or more of the $50 drugwipe tests from an online store and testing yourself at least once to see how you go, because of all the individual factors. It has to be money well spent if it saves your licence.
If you are only consuming capsules then I think it is highly unlikely (even 'clinically shown') that the tests don't pick it up, regardless of how stoned you are, but if you use in a way that contaminates your mouth, like tinctures, infused fudges or canna-buttered toast, then the same advice would apply.
Thanks for the response! Drive responsibly, y'all.