When I make batches of BMHs I usually end up with a few duds and some that I call a "seconds" quality BMH.

Some are just asymmetric beyond what I consider acceptable.
Some have rucks in the side walls - a result of uneven PVC wall duct thickness, uneven heating, and me just not paying attention.
Some have splits in the outer edges beyond what I consider acceptable
OR
all three of the above.

I have tested out some of these hoods and while they are not as good as the "firsts" quality BMHS they are still far better than other hoods or open ducts.

These are free to anyone who is willing to come and pick these up - sorry I'm not posting them anywhere.

There are 3 x 6" hoods and 1 x 4" hoods.

Don't reply here - PM me if you are interested