Never tried the combo, but I have noticed fentanyl to lack some of the true opiate euphoria I enjoy so much, yet it does produce I pretty deep nod easily. Doesn't last long. Heroin is heroin, a true opiate with true opiate effects, also sedating. Since opioid + opioid = more opioid, I don't see why you can't give it a try if you are cautious with the fent as you always have to be with fent. Be cautious with the H too, obviously. I believe, but am not sure, my mother would often suck the Actiqs on top of her MS-Contin. She seemed to like it, I guess. My guess is that the combo would be best with less fent, so as to be used as a "booster" to the H, probably get a little more sedated/noddier than usual and feel good. BE CAREFUL, as always.