Reply by fivecodys

Not sure I understand the issue. You are going to leave the black piece we see in the photo connected to the blower, right? It has a 5” diameter fitting, right?
If so then you need a 5” elbow to mate with the exhaust side of the blower, right?

Like this?

If so, I used a adjustable 5” elbow I got from my hardware store used for exhaust pipe on gas fired equipment. I think I paid $5 for it. I needed it to be adjustable because I had part of the garage door hardware to contend with.
You’ll have to tape all the seams when you install it because it leaks like a sieve. :)

I hope this is helpful.

-- A bad day woodworking is still better than a good day working.