Hi,
here how I got it to work:
I used gimp-print 4.2.7-pre1 and changed gimp-print-4.2.7-pre1/src/foomatic/foomatic-generator at line 209 where it says:
if (m!^\#\s*gptofoo\s+([^\s]+)\s+([^\s]+)!) {
into
if (m!^\#\s*gptofoo\s+(.*)\t(.*)$!) {
(in other version perhaps another line...)
and changed in src/foomatic/foomatic-printermap the space between column 2 and 3 into a tabulator. It was much work and if you don't need an up-to-date version you can download mine here:
http://www.unforgotten.de/div/foomatic-printermap
Hope it works for you too...
--Frank