Hi Chuck,

If at all possible ... it is best to AVOID using extension bars. I have been advised by an expert, that he keeps his stack of cwts as close to the upper bar as possible, and even retained his old, shorter, AP-1200 cwt bar. He says that with the large mass of cwts down the bar, their "inertia" can affect the "responsiveness", of fine guiding corrections.

Of course, this won't pose a problem for those at low latitudes, but those in higher latitudes may have no choice but to use extensions, since the cwt diameter can clip the mount post-meridian, especially the mount AZ Adjuster knob, which sticks out a bit further, beyond the pier perimeter.

Some things to consider, before going for lighter weights further own the bar, for the same leverage.
Joe Z.