Although I certainly agree with the advice of not going over the 400mg level, given the risk of seizure and whatnot, I've used up to 1400mg without problem, albeit being pretty out of it.
I find the drug to be most useful in terms of it's potent antidepresant qualitites. Like THE BEST ANTIDEPRESSANT EVER!
Can't really speak to the methadone issues. Was the first opiate I ever took, and loooooooved it, I only have used something like a collective 20 or 50mgs over my entire life, which I know is nothing in comparison to what folks in maintain programs are dealing with (shit, I can't even imagine taking 160mgs!).
That being said, 300mg will def help with withdrawals, although you'd probably want to taper as much as possble. Once you're down and feel comphy with the meth you might want to integrate 300-400mg into your routine, then get of the meth completely when you feel comfy, continuing the tramadol of course.
On a side note, I find the ER 100mg tramadol/ultram pills way more effective mg for mg when compared to IR formulations (just remember to crush up the ER taps. For instance, it basically feels better when I'm on 200mg of ER tram than 400mg of IR tram. Of course, this might just be me, but who knows.
Tram would definitely be very useful in detoxing from meth though a handful of people who've done this, one with even a maintenance dose of 160mg, on that for about two years, and even he benefited from what I described. A good support group/system than can help you and that you feel comfotable coming to for help is also a much in this situation, although that whole thing is up to you and you know how support networks work for you (and if not, why not try them out - some really suck though, so just remember to keep an open mind, but yea, I've had some horrible experiences around those lines so, yea...).
Best of luck, but tramadol is definitely a good place to start! BEST OF LUCK AND BEST WISHES > You'll be in my thoughts!
p.s. Given it's SSRI properties, just for the record, I might be a little biased given how much positive stuff it's done in my life. But it did also help a couple friends of mine, so who knows. Might just help, if not also actually help you.
That all being said, good luck!