I've fished Weiss only a few times in the last 10yrs ... so I don't know all that much about it. But, as for a 9" Crappie ... I think you're right, as far as it being on the small size, for eating. Then again ... it depends on the lake - a 9" Crappie, from some of my local lakes, is several ounces lighter (on average) than some 9" Crappie I've caught from some other waters.
Watts Bar, KY Lake & Barkley Lake all have a 10" limit ... and they're fine Crappie fisheries. Small lakes with limited production capabilities may benefit from a 9" size limit. Larger lakes, and especially those with high production capabilities, would probably benefit from a 10" minimum. The F&W guys are probably trying to balance things between the people that want size & those that want numbers. Crappie are cyclic in their size/numbers for several reasons ... two of which are spawn & predation. As far as spawning goes - weather & changing water levels (whether weather related or flood control) can all but wipe out a year class. On the flip side - good spawns create a great number of young, and several years in a row of good spawns could put a strain on the food source of those waters. As for predation - that would be fish eating the young or angler catch rates. A large population of keeper fish means the chance for more people to catch fish in numbers. This, in turn, creates reports of "easy pickins" and could lead to an even greater increase in angler predation. This can decrease the overall numbers of potential spawners, thereby creating a "slow" year or two following the boom year. Lake size & creel limits are set to maximize the potential for ALL anglers ... numbers anglers or size anglers. If the lake can support it, and maintain a good recurring crop of fish, then the limits have done their job. But, conditions are rarely static ... they change from year to year, and sometimes dramatically. It only takes a season or two to make a big difference in the availability of fish numbers or size. F&W Biologists are constantly monitoring the populations of these "favored" lakes ... and adjusting size & creel limits to please the angling population.
Location of certain lakes is also a consideration ... as it pertains to max age/growth limtis. Raising the size limit on a lake where the Crappie don't live so long, would/could be an added negative. It could create so many in numbers, that would never live long enough to reach the size limit (in any appreciable numbers), that it would only serve to overpopulate the lake (and that could, in turn, create the situation of stunted fish & a decrease in the biomass of available forage). It's a big balancing act, and adjustments take several years to make any appreciable difference .. whether it be changing the size limit, creel numbers, or restocking programs. I know we would all like to have lakes to fish, where the "size" of fish came in "numbers" ... but, that isn't always possible. ........... Just MHO ..........cp