Hi Craig,
One option may be to change the finder bracket itself. I think the Orion guide package comes with the dovetail finder base anyway. Looking at the photo of the ES80, it appears to have a similar bracket that my 8" SCT had. I have changed that bracket to the type of bracket that the Orion uses, so that I could fit a better finder and only had to file the hole slot, on the bracket, a bit to fit the existing screw holes, on the tube. You may not even need to do this, as the hole distance may be ok.
Alternatively, you could mount a side by side plate onto your mount, although that would be a rather expensive option. I get most of my mounting hardware from OPT or you can try ADM for a side-by-side mounting plate. A further solution could be to find a single, although they are usually sold in pairs, mounting bracket, like this:
http://www.optcorp.com/sv-r90set-r90...mm-scopes.html
You could then mount the Orion bracket to to that.
Cheers Peter