Genesis Flyer - bad fit?

You've done the following?:

• loosened the new stem clamp bolts (and greased under the heads + the threads)
  
• similar grease for top-cap bolt
  
• checked the height of the stem clamp compared to the old one
  
• made sure there's 2mm to 5mm of stem clamp or spacer protruding above the top of the steerer column
  
• given the front end a wiggle to make sure everything's seated properly
  
  

If so, I don't know what the problem is :P