Jimbo,
Do you have a good doctor? Mine is a fine neurologist Ph.D.
He KNOWS and is a genius with meds. (as Neuro's should be, but some neuro's are simply too egotistical and got into that field so they don't get 'dirty').
Mine also has rsd.
He didn't start me on, (I was with Dr S, and they were partners), Methadone, but, it's inexpensive, and there's No Buzz! Also, it's Very inexpensive. Some of the 'lighter sounding opiods' like those you said you were on, as well as others, can cause myriad side effects that are unpleasant. (I like to feel my feet touch the ground, even though it hurts, I don't want any 'buzz'.

I'm NOT saying that methadone is without risks, but I think most level heads would agree about dependency. When do you expect to be cured of RSD? So, I was taught to take it as I would say, 'Blood Pressure medicine'. OK.
What you need to know, is that it can cause constipation, esp. if you're sedentary, and don't have a good diet. There are numerous ways to correct/control that. Also, you don't want methadone if you have any breathing problems. It can depress your 'breathing'.
So you can go to www.drugstore.com, and other places to look up it's side effects.
When your RSD is cured, then worry about dependency!

Btw, I've been on methadone for 20+ years. My cocktail includes, besides methadone,
Cymbalta, (Nerve pain, depression) Diazepam,(muscle/nervous system relaxant), Zanaflex (it's generic form, muscle relaxant and for sleep), Migraine meds, Lidocaine patches, (only cut in thirds, for my neck / low back, where I have Herniated discs), and my 'head med', Aricept (off label it's for altzheimers, I have a TBI).
I also have TOS, and sleep apnea came with the TBI, so I use a CPap machine with O2 added.

So, as you can see or tell, that my doctor and I spent lots of time, decades experimenting on this cocktail, especially after the 2nd accident, which caused the Head Injury and discs and sleep issues. It's a bumpy road, but taking methadone was an easy decision for me.

I wish you well!

Pete

asb