You want to place them in places they will move to as they work shallow to the spawning grounds. Most are still holding deep it seems so if you place them anywhere from the mouth of creeks in 25' depth up to 10' depth in known spawning grounds you should be able to fish the piles as they move in to spawn and as they move out from the spawning grounds plus you will be able to fish them through the summer as they will use them as holding spots as they move from deep to shallow to feed and as the water gets hot they will tend to hold in the brush. No bad time to set out brush piles.
Good luck,
Ronnie
PROUD MEMBER OF TEAM GEEZER ---------
Ascend 133X 13' - MotorGuide Xi3 & Mercury 4