title_body: Should the filter capacity be matched to the brew amount?
upvoted_answer: I would agree with you.  With the thin flat layer of coffee the hot water is just pushing a hole right through it.  You are not getting nearly the contact time of a full size brew.  
  
  If it was conical or V shaped filter then it would better accommodate different size batches.  
  
  On that pot it does not look like you could just simply use a different filter size.