[bojan]

That must be easy.. Just wrap thick rubber around the tube (there are places selling various rubber product.. and rubber is pretty heawy).
Another alternative is to move the tube forward in the mount - it depends how the tube is attached to the Dec shaft.
Could you post some images of your scope?

I had similar problem with my dobson when camera is attached, and I solved it by adding brass weights (0.5kg) just under the mirror.
Also, I have a steel shaft (8mm dia) running in parallel with the tube, with movable weight (again, brass block). So I am ready for any eventuality :-)