With red-faced embarrassment, I now suspect that I was absolutely wrong in my answer above. I looked at 4 different Cub-22
mowers. 3 of them had the flange turned up, 1 had no wear plates
at all. I found some old, badly worn, wear plates
in the junk pile. They had been removed and replaced from a mower 30 or more years ago. The rust pattern on them clearly showed that the flange was down. The arched knife clip rust pattern on the wear
plate was unmistakable. And it seems very likely that those wear plates
were the originals on the mower, much more likely than any we would see on a mower today.
So I went to one of the largest farmers in this area. Has two BIG combines, etc. He says that the flange goes down, that he has never seen it any other way. Pulled one of the plates
from his parts bin and it is exactly like the ones on the Cub mower!
I am seeking confirmation from another source. Hopefully next week, I can actually test it on my mower.
Needed a few more parts for the mower today and went to the implement dealer. Many parts for sickle
mowers have more than doubled in price since last year. For hobbyists, that is one thing. For farmers, it is another thing entirely. Food prices will continue to rise.