gpxelinux.0 - http proxy support?

Great to see gpxelinux.0 support http file transfer in addition to tftp.
Is it possible to specify the use of an http proxy, too?
If yes, how would that be done.?

My /tftpboot/pxelinux.cfg/default file for gpxelinux.0 currently
looks like this:

  label linux
  kernel memdisk  
  append initrd=http://192.168.1.1/mydisk.img

Thanks,
   Marcus

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