I hope I am not trying to teach my grandfather to suck eggs here.
I have never seen a Dob up close but the problem here seems to center on the mechanics of moments. Its a bit like a see-saw.
The extra weight of the camera is a longish way from the Pivot point or the bearing of the truss therefore its extra weight is amplified.
The moment or effective extra weight the camera imposes is equivalent to its weight muliplied by the distance from the bearing times the Cosine of the angle of elevation of the truss. As the angle of elevation increases to the Zenith the Cosine value decreases and so does the moment of the extra weight.
(If you were to imagine the point vertically below the camera on the ground ie where a plumb bob suspended from the centre of mass of the camera would touch the ground -then the distance from this point to the bearing's horizontal location times the extra camera weight is the moment created by the camera).
To counter balance this you either attach a suitable weight below the pivot / bearing OR above the bearing with an opposite sense and equal moment.
Strapping an arm to the truss at any point below the camera mount and with a suitable weight on its end should counterbalance the camera weight.
If the truss is pointed due North at 45deg elevation then the arm should point due South at 45deg.
If the arm is light eg Aluminium then adjusting the point at which the counter weight is attached to the arm and the point of attachment of the arm to the truss can be used to fine tune the assembly.
Contact me privately and I can do a diagram with some real values if you want
i have been using a canon rebel xti (us) 300d (europe) it does not belong to me neither does the photographer attached to it. but since he knows how the camera works i thought id let him come along .with either the 5" newt or the 127mm mak any thing less than 2 sec exposure yielded black screen results save for the moon, does the 10" aperture of your dob collect enough light to compensate for such short exposures. just curious. shiva
my ext is a f/15 id like to get the moon fully framed but im not sure which focal reducer value to use any suggestions. seems like there should be math for this. my local shop has a 6.3 i think , also a generous return policy. any suggestions. shiva
  