SSH_FXP_STATUS messages block for an inordinate amount of time

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When I upload via SFTP with FlashFXP or Mindterm's FTP<->SFTP wrapper,
I'm able to get upload / downloads speeds of around 500kbps.  When I
try it with my own SFTP implementation, however, my upload speed is
cut in half.  My question is why?  When I upload, I send one
SSH_FXP_WRITE message of packet size (16384) size and wait for the
SSH_FXP_STATUS message back.  For a 1mb file, that's 64 SSH_FXP_STATUS
responses.  Problem is, a lot of these SSH_FXP_STATUS messages block
for a tenth of a second if not more.  By itself, a tenth of a second
isn't a whole lot, but they add up fast.  Indeed, the twenty-two most
time consuming messages to either send or receive are these
SSH_FXP_STATUS messages and in all, these twenty-two messages are
costing me 2.89 seconds.  For a 1mb file, 2.89 seconds is a lot.

Any ideas as to what the problem might be?

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