Hmm 1 kg is going to be pushing it. Maybe some sort of side by side mount to keep the center of gravity as close to the head as possible. But then your will be adding extra weight in the form of dovetails and mounting saddles. I've just recently bought a 76 mm copy scope that shouldn't weight more than a kg or so (I could weight if you want). There might be a few of those around on the astromarts somewhere.
I can well understand you dilemma John as I was going through the same issues with trying to mount an 8" sct and the Orion 80ED on my Losmandy GM8. If you haven't read any posts in the pic of your equipment thread I made mention of your counterweight shaft attachment. I really wanted something like that to solve my problems. I eventually went for a side by side setup and found a small 60mm refractor to use as a guidescope rather than the 80ED. It was pushing the limit photography wise (not as much a you are though) but at least everything was in close to the head. I also had more counterweights made to shift everything up the CWS, again to bring as much weight in close to the head as possible. My solution in the end was to buy a G11.
I know but I couldn't help myself
