The MDC stocks Stockton every other year with hundreds of thousands of walleye fry. It takes about two years for the fry to reach the 15"minimum. The MDC considers Stockton a "put-and-take" fishery because natural spawning success is very limited. The result is that small fish dominate the size distribution; with the smaller minimum size (15") and high attrition, there number of fish making it to that 25"-plus range is significantly lower at Stockton than at other lakes.
They are there, however. The shad forage base supports growth at all stages, and I believe the lake record is 16 lbs. The really big fish are just few and far between.
I've been fishing Stockton for walleyes for 15 years and still have not caught an 8 pounder there. Then again, I prefer not to fish for pre-spawn eyes (I wish they'd close the season down here to protect the spawn, but as long as it's legal I don't begrudge anyone else fishing for them). If I felt differently and was determined to catch a large eye at Stockton, I'd do as bfishn and Josh suggested and concentrate on the late winter/early spring period, throwing suspending stickbaits to the mainlake points from midlake to the dam
Otherwise, you'll only catch the occasional larger fish mixed in with the eaters. There are some largely unexplored patterns to investigate through the rest of the year, such as exploring the many acres of timber or finding shallow springs or current that could hold some big fish, but they'd take a lot of time to unravel.
In general, think Stockton for numbers, the border lakes for trophies.