http://www.picbasic.co.uk/forum/showthread.php?t=543

when setting the fuses in code space you will need to comment a couple lines in the PIC's Inc file. While you are doing that look at how the fuses are set(single line, double line). Simetimes it does not matter but sometimes it does. Depends on the PIC.

So looking at how it is done in the Inc is the best way to know.