21" scoop design

blue one looks right.....

Done. Thanks Bee.

Hehe I was thinking that it probably was something like that

About the corners, at these wavelengths and with these dimensions its all about the volume. Its hard for me to see, but you need to make the "brown" piece so that you keep the volumetric expansion as uniform as possible. And most important, don't change the throat point.
What is the narrowest point now and where are the second narrowest point located?

Gonna try and improve it a bit.....

this has better expansion....

This is even better-

Getting used to this program (sketchup) ,......it's pretty wicked

My money is on the one with the most sophisticated corner, but the difference in sound might not justify the more difficult build. Only way to know is to test of course

Well, it would be quite easy to build the cabs without the brown and green bits and add them after. I could make 3 or more different ones and run some tests or something.....

I guess that is up to you if you feel like experimenting