You really should be fine in this practice. Of course, it must be noted that dealing with high-dosages of Opioids are potentially dangerous and/or lethal, but to anyone using Opioids, this should be common knowledge. Methadone is most dangerous to individuals who do not fully understand the nature of the drug. It's a powerful Mu Opioid agonist just like Heroin/Morphine, but the major pitfall for folks is in an incorrect estimation of Methadone's timeline of effects. The onset of effect is typically 1-2 hours and in my experience, it can take as long as 5 hours to hit the drug's true peak.
There is also the issue that a longer onset and slower elapsed time to the peak of intensity can cause users to inaccurately estimate their level of intoxication. It's my and others' beliefs that this is the primary cause of overdose, although there is some information out there that also implies that Methadone itself causes a dose for dose higher degree of respiratory depression than other similar Mu agonists, but this appears to be conjecture.
You know your body the best, so just don't go overboard. I will say, that in many Heroin Maintenance programs in Europe, in which users receive a standard dose of Heroin multiple times per day in a similar fashion to a Methadone Clinic, it's common to prescribe coinciding quantities of Methadone in an attempt to keep the patient as stable as possible throughout the evening until they return for their morning dose. So, the practice in general has some clinical acceptance.
Are you getting high, maintaining or otherwise what combination of the two describes your current usage and how Methadone effects you when you take it?
If 2 Grams of BTH is your average intake, 50mg Methadone should be a pretty appropriate dosage for you. It obviously depends on the quality of the Heroin, but you could probably handle more Methadone. At any rate, 50mg should definitely keep you straight and functional.
