I've done methadone clinic twice,the 1st time for 3 and a half years and the 2nd for a year.Both times I topped out at 100mg since I had a huge dope habit both times.The clinic in my hometown starts everyone out on 30mg.The clinic doctor does an evaluation where he asks how much dope you take per day and they just take your word for it.They raise you up to a blocking dose(where you can't feel dope anymore)pretty slowly and gradually so you never get a true high from it,just a nice,pleasant,warm "glow"that lasts throughout the day.It's subtle,especially if your used to iv heroin or more conventional opiates since methadone has a slow absorbtion rate.The clinic doctor told me it usually starts to kick in after 30 minutes or so and peaks at around an hour for most people.I found this to be true for me as well.
When I wasn't on the clinic but had a raging,bundle and a half a day habit(as did my girlfriend) we found that 40mg would still keep us well for 24 hours.Once,when she had gotten ahold of a bunch of 10mg pills we decided to take 80mg each,neither of us having done methadone regularly for a while nor having taken a large dose for a while but,as I mentioned,we had pretty good sized H habits.80mg had us both high as shit.Nodding,burning ourselves with cigarettes,taking a sip of water and shortly throwing it up etc....So IME,even with a large habit on dope,a good sized dose of methadone can still fuck you up.And it was very euphoric.Neither of us wanted any dope that day,we were perfectly high and content.Both of us were glad we didn't take more than 80mg and neither of us thought it would get us that high.Both of us are also quite experienced at mixing benzos with heroin,methadone and other opiates but we were glad we didn't take any Xanax or Valium that day,even though we had a good ammount of both as well as a few Ativans.So,given your stated tolerance levels and frequency of use,I would start with a single 10mg pill and see how you feel after an hour/hour and a half before I even thought of taking more.Remember,methadone can be very subtle compared to oxy,dope,or whatever so you may be higher than you realize,very similar to the way people take benzos and don't realize how fucked up they are.Speaking of which,I would be very careful about taking any benzos with it untill you are good and familiar with how the methadone effects you.That combo has taken a lot of people out of the game and I would imagine a good pecentage of them never really knew just how fucked up they were.I would also advise you,as others have,to limit how often you dip into that bottle since a methadone habit can sneak up on you very easily before you even realize your entering addiction territory and the withdrawls last and last.IME they aren't as intense as dope withdrawls but last way longer and still are intense enough to suck plenty.With all that said,have fun with your find you lucky dog.I would love to discover a forgotten methadone script in my medicine cabinet lol.Don't forget the laxatives.When my girlfriend started on the meth clinic she didn't shit for like a week and finally had to buy an enema.I never had that problem but maybe that's because I drink a shit load of water throughout the day and tend to snack on apples and dried fruit trail mix.I'll say it again,damn I'm jealous lol.