Did a little research last night and had new idea about the U channel.
Maybe it's metal edging?
http://www.grovems.co.uk/standardsections/index.html
View attachment 796902
Closest match I see here is around 50% too tall, but the stuff looks close.
Most U-channel is too squared off.
This is the last piece I'm missing for mine. It'd be nice to do in metal.
NIce find! The u channel on the prop was 1/2" by 1/2" yes?