I don't have any personal experience with subs but while I was on about 400-500 MME a day of fent,oxy, and norco I've read a massive amount on it (some on this site, some from online articles) and you definitely need someone with personal experience to help you on this and I hope someone here will.
That being said, what I do know from other accounts is you need to drop from 8mg to 2mg as quickly as possible. The jump from 2mg to zero is SUBSTANTIALLY more difficult than the jump from 8mg to 2mg. Along with this, the quicker you go from 8mg to 2mg = the longer you have to wean yourself down.
Assuming you had no taper in place and originally spoke of 5 weeks at 8mg. You would have 20 weeks at 2mg instead.
To add to that, you shouldn't take the full 2mg the whole time either, you should be tapering. Which means you could probably stretch what you do have to a year.
As far as schedule, I have read one on this site a couple years ago so I know it's here. Someone with better knowledge of this site could probably help you find it but it's basically something along the lines of...
Step 1: Get to 2mg as quick as you can. This lower dose shouldn't help a bunch with cravings but should not put you in a bad withdrawal either.
Step 2: every week or two cut the dose in half until your down to 0.25mg, even then, attempt to cut those in half to the best of your ability. And reduce until you literally cannot half a dose anymore. Most people I read about didn't have issue after cutting 0.25mg in half for a few weeks then jumping off.
Like I said, this is from what I read ON THIS SITE. An actual schedule is here, and people with first hand account of going through this is here. If either have different knowledge/advice then listen to them, not me. I'm just trying to help in case no one else does.

good luck.