On my setup the template overrides don't appear to be working.  Maybe I have to enable this somewhere?

I am familiar with template overrides and use them extensively (thats not to say I didn't miss something here). 

I have done as explained in the directions:

So you can either choose to use the versatile base styling of the plugin or simply override it (both the HTML and CSS code) by copying the plugin's folder /plugins/content/jw_sigpro/tmpl/SomeGalleryName ... in Joomla! 1.6 or newer TO your Joomla! template's /templates/YOURJOOMLATEMPLATE/html/jw_sigpro/ folder (create it if it doesn't exist), as you would with components and modules. Whatever changes you do from now on within this folder, will completely override the plugin's output, exactly as you would with any other MVC component or module.

In my case I have copied the contents of
/plugins/content/jw_sigpro/tmpl/Galleria
to
/templates/rt_radiance/html/jw_sigpro

When I edit the file /templates/rt_radiance/html/jw_sigpro/default.php it does not override the gallery template and the gallery selector in the plugin settings still works (it should have no effect now that I have my own override).  What am I missing?

Does anyone have these template working?  Can you look at my paths (listed in previous post) and see if they match yours?  I did this the same way as as with k2mart which does work, but with SIG it does not.

Your template should take the place of Galleria in your overrides.

Are you saying that the path for the overrides should be /templates/rt_radiance/html/jw_sigpro/Galleria  ??  That doesn't work.  I have tried placing a modified default.php in both /templates/rt_radiance/html/jw_sigpro/Galleria and /templates/rt_radiance/html/jw_sigpro and neither has any effect on output.

I would like to clarify that k2mart uses the same format for overrides and it works perfectly.  Is this a problem with SIG Pro v2.5.7?

Does anyone here use template overrides with SIG 2.2.  Does it work.  Can you help?  Please?

The overrides should be in
/templates/rt_radiance/html/jw_sigpro/the folder with your  overrides.

i think template should take the place of Galleria as well

No, if you use overrides this is not necessary...