Can I simply change UNITS and EXTENT in PROJECTION?

[mark at deblois.nl]

Hi all!

My mapfile successfully outputs a map in Winkel Triple projection using
the parameters below. Extent BBOX units are in meters as this is what the
projection seems to output.
What I would like to do is change the units to DD and set the EXTENT to
-180 -90 180 90 (world view DD) but when I do so I get an empty map. Can
anyone tell me if what I am trying is possible? And if so what I am
missing (perhaps the obvious)?!

Thanks for your help.

cheers,
Mark

PROJECTION
  "proj=wintri"
  "ellps=WGS84"
  "lat_1=50"
  "datum=WGS84"
  "units=m"
# this is what I'd like it to be in  "units dd"
END

SIZE 600 400
EXTENT -20000000 -11000000 20000000 11000000
# this is what I'd like it to be in EXTENT -180 -90 180 90