The logic for feeders is that when markets are rising, sell as fast as you can to grab the profit and to refill so you can make another turn; and when markets are falling make them heavier so more pounds = more dollars.
The problem is that it only looks at the revenue side and not at all on the cost side.
When cost of gain is figured in, you should sell heavier weights into rising markets because the margin per pound (difference in cost of gain and market price) is greater.  When markets are falling, cattle need to be sold lighter because the margin between cost of gain and market price is shrinking and often gets upside down.  Right now, if your cattle are much past the average days on feed (which varies by start weight) you are loosing money on every pound you put on because the cost/pound of gain is greater than the pay price.
Don't get confused by the cost of gain pay weight to pay weight (like on a projection or closeout), I'm talking about the cost to add each additional pound when the cattle are already finished.  
The other problem with selling heavier weights into a falling market is that it plays right into the packers hand.  At times we are not current as a feeding industry the packer is in the drivers seat and dictates what he will bid for the cattle.  When we are current and our backs are not up against the wall to get cattle moved, the packer has to bid up more to shake cattle loose.