Flue brush size and rods

I need to buy a flue brush and a set of rods. My flue measures 7 1/4 inches square on the inside.
Would it be best to get a 7 inch brush rather than an 8 inch brush?
I will need enough rods to reach 36 feet. Would it be best to get 3/8 inch diameter rods rather than 1/4 inch?
I expect stiffer rods would handle better at this length.

PaulF

I will have to vote for the larger size brush. I cleaned my chimney before installing the liner. The flue was also an "in between" size. I started with a slightly smaller brush, but after a few feet, you have no effective "scraping power" on the walls, so I got the bigger brush. That did fine, the only issue there is that it was a one way trip. The bristles were long enough and stiff enough that they would not reverse in the chimney.

I wound up going the cheap way and using a rope. Had to make extra trips to "reset" the brush because I couldn't push and pull with the rope, but I only did it once so not too big of a deal.

There are some pro sweeps on the forum too, so maybe they can offer even more insight!

Good Luck
Corey