I have seen small weights taped onto the OTA near the primary. These can also be used with velco to make it easy to adjust for different loads.
If you want to go for a fancier solution this might give you some ideas:
http://www.bintel.com.au/Accessories...3/catmenu.aspx
The system shown in the link is for Meade Lightbridge but you might be able to alter it to suit your scope.