If you can't or won't spend time in fixing compline/d_gconvert.U, the best approach will be to create your own Policy.sh which defined d_Gconvert exactly as you want it.
The -D argument might work, but I am always scared of interpolation when requiring quotes. The tricky parts are the callback units.
Setting this using env does not work.
Enjoy, Have FUN! H.Merijn