If your 1600GTO mount is is frequently used as a portable mount, you may wish to consider upgrading to this counterweight shaft adapter. The stainless steel insert will reduce the likelihood that you will damage the threads by cross-threading when you attach your stainless steel counterweight shaft.
This countershaft adapter can be used on all 1600GTO mounts with or without absolute encoders.
Installation Instructions: Simply remove the original counterweight shaft adapter and install the new one. Note that both components were designed with a through hole into which you can insert an object, like an Allen wrench, to either loosen or tighten the adapter.