I'm on 40-60mg of oxycodone/day and when I switch back to hydro(for when I run out of oxy) it takes me at least 80-100mg to get a decent buzz. I also have a bit of an infrequent heroin habit that may contribute to my tolerance though.
Compared to everything else you're taking the Vicodin is going to feel like nothing. I started with hydrocodone in my opiate career, but after going through fent, codeine, oxy, heroin, and others, the Vicodin feels like I'm taking Tylenol III's now. I imagine you're in a similar spot. If you're just on the fent and not taking the methadone and MS Contin, it's going to take at least 50-60mgs to get you anywhere. Start small and work your way up safely.