What SIZE crankbaits for BIGGER fish? Small, Medium, or Large?

[cheesehead]

I own most of the crankbaits I use for trolling in at least 2 or sometimes 3 different sizes. After many years of very unscientific experimentation, I've decided that, in general, I'm catching larger fish on the smaller baits. Has anyone else experienced this? I use the Precision Trolling book to put the baits at the same depth, and have upgraded many times to the next larger size of a particular bait (same pattern, of course), only to catch the same size or even smaller fish! It seems, at the end of the day, like the larger fish usually come on the smaller crankbaits. Is this just coincidence, or dumb luck, or does anyone have a reasonable explanation for this phenomenon? Just lookin' for opinions . . . 'cheesehead'