I owned a Mirage built Kirby 25 and raced extensively against a well sailed Kirby 30. My Kirby 25 was a very early boat and while very simply was a very well constructed boat. I have been aboard a later Kirby 25 that did not seem as well built. All of the Kirby 30''s that I have been aboard seemed to be well constructed but I have never had a chance to spend as much time on Kirby 30''s as I have on the 25''s.
As to racing, the Kirby 30''s were competitive in a pretty wide range of winds in PHRF and MORC. Here on the Chesapeake where winds tend to be light, several of the Kirby 30''s were converted to masthead
rigs which made them even more competitive. For light air lake sailing I would see if you can find one of the masthead boats although the fractional rigged boats were no slouch. They certainly should be more competitive than your Columbia Saber
Jeff