Question on converting TIFF to ps using convert

Hello all,

I am using the linux/unix "convert" command to change FTP'd DiFAX maps into 
Postscript files to print them. Since an upgrade to Redhat 7.3, the output PS files have 
grown from ~1.5 MB to 13 MB. Is there any way I can make them smaller? My printer (HP 
LaserJet 4000) is choking on them due to the large size. Any help greatly appreciated.