[Kube]

Milt, Thanks for the great photographs and thanks especially for your patience with me. As winter approaches and the daylight becomes short, I tend to make the most of all daylight and as such don't typically get in until late.
Anyway...what you have appears to be correct. That hole in the channel with no corresponding hole in the bracket is absolutely correct. Originally, when the top mechanism was installed and properly adjusted, a hole should have been made in the bracket and a screw installed in that hole you are questioning. I have little doubt that in the reality of a fast moving assembly line, this didn't always happen.
It should have.
As far as the channel seeming too long... well, if the top mechanism is adjusted properly, those channels are not too long.
I can tell you from a lot of experience (this is my fourth convertible restoration) that the top mechanism is a total pain in the butt to fit properly. Yes, a guy can get it to fit okay and operate but to make it fit well takes a lot of time and patience.
To reiterate my earlier comment, this "requisite patience" was most surely lost on the assembly line.
Just recently, I'd spent nearly 28 hours adjusting my top mechanism and I must say, it fits perfectly. However, I no doubt lost a little hair in the process. Lord knows my patience was tested numerous times.
If you are satisfied with he way your top mechanism fits, I might suggest you trim the channel(s) as necessary.