This will require the call
dvidvi -m4:0(0,0),1(7,0),2(0,10.5),3(7,10.5) infile.dvi outfile.dvi
to dvidvi. The offsets are a little different this time but experimentation showed that these are best for this format, at least on the LJ5 series. Now the call to dvilj will have to be
dvilj -m#500 outfile.dvi
Be warned that changing the magnification means you'll need different bitmap fonts. And
you thought you could give 
a rest for a while...
A word of advise on thumbnail printing: you should really use this only if your printer
can deal with 600 dpi or the document has rather large print. The deficiencies of 300 dpi
printing will become painfully obvious the smaller your fonts are getting.