Here's one possible solution:
Load the boot into your scene, select it and go to the Set Up Room. Select the boot once you're there and make sure you see something like "M3 Boot SETUP" on the parameters palette. Then simply translate the boot down the Y axis slightly, go back to the Pose Room, conform it to Mike and see how it looks. This is what I usually have to do with footwear.
Just out of curiosity, how many bones are you using?