Mike
I would say that using the larger baits turns the odds in your favor of getting that 20"+ bass. I consistently catch larger bass on larger baits. I have caught them on 1/16 oz. jigs as well, but not as often. If you aren't keeping a big spinnerbait in your pack, you could be "missing the boat." I would say that a tandem white spinnerbait has caught more 18" plus bass for me than any other lure. A big topwater, buzzbait or crankbait works well too. When I work a finesse approach, lately I have been throwing 4" tubes or bigger.
Being in big fish "habitat" is also a plus. To me, this usually means the right combination of structure and depth. The deeper water seems to be the key. There is a stretch of the WI River I have been fishing for close to 15 years (?). It sees a lot of fishermen and the big girls are not so easily fooled. Getting off the beaten path helps the odds in this case. But, knowing the fish are there, but wary, keeps me interested enough to keep plugging away. I'm not a live bait guy, but a live craw in this situation has helped saved the day many times when a mile downriver, they will more eagerly hit an artificial.
I also like fishing the rivers when they are up a bit and a little off color. I think the stronger current really shakes them up and gets them on the feed for awhile.
How are you guys measuring fish to the 1/4"? Isn't that an automatic roundup to the next whole inch? That's the way the USPS does it! From the butt of my rod to the first wrap is an even 18". That's as close as I ever measure. I tack on the inches as I see fit.
I am an estimator by trade after all!
Don, that is a sweet bass!