Steve,
I'm not really sure what your looking for here.
To me it seems that you want to see things a little better than the 80 mm will give you.
Your 8" Dob will do that, but you have never seemed that happy with it.
What about a 8" sct tube on your EQ5 mount!!!
It would be better than a 100mm and the EQ mount will hold the short tube ok for viewing.
Dew will be a problem but a flexishield can fix that. You have a diagonal etc, so you just need the tube and dovetail plate.
I came close to doing the exact thing, but found the Mak instead.
