I have no experience with synthetic cannabinoïds, but from what i've read about them, they cannot be considered to be as safe as weed. I do know from experience though, that extremely large amounts of cannabinoïds do in some kind of way mess with you dopaminergic system. There is a method i sometimes use to get incredibly stoned. You might want to try it, because maybe it's better for you than synthetic cannabinoïds, but there is a side effect..You basically let hash or powdered weed dissolve in something like olive oil, or hemp oil, or any other kind of fat, and swallow all of it in one take on an empty stomach. So the trick is to get as much cannabinoïds in an as small as possible amount of fat. When i start taking more than 1.5 grams, i do get hangovers though, or rather, i feel very tired and exhausted for the next two days.