Thanks guys. I did make a spreadsheet for this, but I assumed the FOV of the zoom was 50 at 20mm and 24mm, and 68 at the shorter FLs. I think that's roughly what it is. By the numbers, it seems as though the AFOV is substantially improved at the longer zoom FLs...to the point it may exceed the capability of the optical back's 1.5" opening even.

I was wondering how it might look in actuality though, if the numbers lie.

It is at the lower powers where I was hoping to get an especially wider view with the reducer, to help compensate for the zoom's narrower FOV there. I know this zoom EP is not supposed to work as well with faster scopes though, but I think the 8 SE at f6.3 is supposed to be borderline OK (??). I guess I'll find out, I ordered the reducer anyway...the gear shop phoned while I was making the post and I thought what the heck. I am pretty sure there are some factors here that I don't know about: I don't actually believe

that the reducer will improve my low power AFOV beyond what the zoom itself can do...that's how little I know about real-world optics.