Well ... I DO tie a bow-tie knot on top of the cord-lock and then stuff the laces.  No slippage then and the knot stays tied.  

Before the cord-lock, even a double bow-tie knot came loose on the flat laces of the OTB's.

But, you need to go with what you have confidence in.  The LAST thing you want to worry about humping a load down the portage is whether or not your boot laces are tied.

dd