Glen
Never feel bad about having a go at making your gear better! It is the best way to learn how a scope works and how to get the best performance out of it.
The obvious thing to do is to wind the mirror back in the tube. I did the same thing when I bought a 10mm Ethos and found it wouldn't focus. (imagine how I felt with a $700 ep!!
) Anyway I had to move the primary up the tube so I just wound it out 1 turn at a time on each knob in sucession, checking the collimation and focus every 2 or 3 winds until it was ok.
As it was the opposit problem the solution was a TV High Hat adaptor. In your case, wind the mirror. If that doesn't work, try shorter springs. Another option is the springs supplied by Bob's Knobs. (see
http://www.bobsknobs.com/Newt/page57/Z12.html these are for Zhumell scopes which is what GSO dobs are called in the US) These are what I used and they worked a treat. Not sure who sells them these days in OZ.
Malcolm