I like the way you think.
I have no experience in intentionally selecting white crappie for unisex ponds, however I'm in agreement that a male white crappie in spawning mode turns almost jet black in some waters. The fact that it's a one acre pond makes this a compelling question. I really wish you'd try it, but remember the old adage "When in doubt, throw it out". I guess in this case it's "When in doubt, fry it up".
...and a light squeeze of the ol' abdomen might give you a clue as well.
